KaraZajac
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Promotes refluxfs (CVE-2026-64600) to a 🟢 full-chain module. VM-verified end-to-end on Rocky Linux 9.8 / 5.14.0-687.10.1.el9_8.0.1.x86_64 under qemu/KVM, unprivileged uid=1000, SELinux Enforcing: skeletonkey --exploit refluxfs --i-know --full-chain reflink-clones /etc/passwd, races the CoW window (32 writers / 8 helpers), strips root's password field on-disk (root❌ -> root::, the public PoC's technique), evicts the stale page cache, verifies via O_DIRECT and returns EXPLOIT_OK. `su root` (empty password) then gives uid 0. 3/3 wins on a private-extent target (1244/3716/7913 rounds, 4-30s). Safety properties (this bug rewrites the block device permanently, unlike the page-cache 🟢 modules): - Crafts the payload FIRST and refuses unless it can preserve both root and the invoking user's line; every other passwd line is kept byte-for-byte. A tail-truncating port drops sshd/nobody/the caller and bricks login (hit exactly this during development). - Backs /etc/passwd up before the race; restores on failure; cleanup() restores it (run as root after the pop). - Destructive path gated behind --full-chain. Plain --exploit / --auto run only the safe own-files trigger (EXPLOIT_FAIL), unchanged. Exploitability constraint discovered during verification (NOT in the Qualys writeup): the race only fires when the target's extent is PRIVATE going in. The block starts at refcount 2 (target + attacker clone), the concurrent CoW drops it to 1, and the stale writer reads "1 -> private". A file already reflink-shared with a third file keeps a post-CoW refcount > 1 and is NOT attackable via that target. Stock Rocky 9 ships /etc/passwd pre-shared and was unattackable across ~41,000 rounds; rewriting it to a private extent (byte-identical content, as any useradd/passwd/vipw does) made it fall in ~2,000 rounds. So the exploitable state is the normal administered state. Also fixed a page-cache staleness bug in the win path: the overwrite bypasses the target inode, so its clean cached pages are never invalidated and a buffered read (getpwnam in `su`, or the module's own verify) would see the OLD passwd. The module now issues POSIX_FADV_DONTNEED on a win and verifies via O_DIRECT. detect() --active gains a per-target extent-privacy check: it reports whether /etc/passwd is private (attackable) or already-shared (not). 88-test unit harness still green (148 total). Docs updated: MODULE.md (full-chain flow, private-extent precondition, verification tables), NOTICE.md, CVES.md (🟢 + tier/ops tables), README (15 full-chain / 13 primitive; lands-root list), RELEASE_NOTES, targets.yaml. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0118iUgHY44hdRtANgyCmu7y
336 lines
17 KiB
Markdown
336 lines
17 KiB
Markdown
# SKELETONKEY
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[](https://github.com/KaraZajac/SKELETONKEY/releases/latest)
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[](LICENSE)
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[](docs/VERIFICATIONS.jsonl)
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[](#)
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> **One curated binary. 46 Linux LPE modules covering 41 CVEs from 2016 → 2026.
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> Every year 2016 → 2026 covered. 29 confirmed end-to-end against real Linux
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> VMs via `tools/verify-vm/`. Detection rules in the box. One command picks
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> the safest one and runs it.**
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```bash
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curl -sSL https://github.com/KaraZajac/SKELETONKEY/releases/latest/download/install.sh | sh \
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&& export PATH="$HOME/.local/bin:$PATH" \
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&& skeletonkey --auto --i-know
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```
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> ⚠️ **Authorized testing only.** SKELETONKEY runs real exploits. By
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> using it you assert you have explicit authorization to test the
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> target system. See [`docs/ETHICS.md`](docs/ETHICS.md).
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## Why use this
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Most Linux privesc tooling is broken in one of three ways:
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- **`linux-exploit-suggester` / `linpeas`** — tell you what *might*
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work, run nothing
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- **`auto-root-exploit` / `kernelpop`** — bundle exploits but ship
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no detection signatures and went stale years ago
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- **Per-CVE PoC repos** — one author, one distro, abandoned within
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months
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SKELETONKEY is one binary, actively maintained, with detection rules
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for every CVE in the bundle — same project for red and blue teams.
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## Who it's for
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| Audience | What you get |
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|---|---|
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| **Red team / pentesters** | One tested binary. `--auto` ranks vulnerable modules by safety and runs the safest. Honest scope reporting — never claims root it didn't actually get. |
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| **Sysadmins** | `skeletonkey --scan` (no sudo needed) tells you which boxes still need patching. Fleet-scan tool included. JSON output for CI gates ([schema](docs/JSON_SCHEMA.md)). |
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| **Blue team / SOC** | Auditd + sigma + yara + falco rules for every CVE. `--detect-rules --format=auditd \| sudo tee …` ships SIEM coverage in one command. |
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| **CTF / training** | Reproducible LPE environment with public CVEs across a 10-year timeline. Each module documents the bug, the trigger, and the fix. |
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## Corpus at a glance
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**46 modules covering 41 distinct CVEs** across the 2016 → 2026 LPE
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timeline. **29 of the 41 CVEs have been empirically verified** in real
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Linux VMs via `tools/verify-vm/`; the 12 still-pending entries are
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blocked by their target environment (legacy hypervisor, EOL kernel, or
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the t64-transition libc rollout) or are brand-new additions awaiting a
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VM sweep, not by missing code.
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| Tier | Count | What it means |
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|---|---|---|
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| 🟢 Full chain | **15** | Lands root (or its canonical capability) end-to-end. No per-kernel offsets needed. |
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| 🟡 Primitive | **13** | Fires the kernel primitive + grooms the slab + records a witness. Default returns `EXPLOIT_FAIL` honestly. Pass `--full-chain` to engage the shared `modprobe_path` finisher (needs offsets — see [`docs/OFFSETS.md`](docs/OFFSETS.md)). |
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**🟢 Modules that land root on a vulnerable host:**
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copy_fail family ×5 · dirty_pipe · dirty_cow · pwnkit · overlayfs
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(CVE-2021-3493) · overlayfs_setuid (CVE-2023-0386) ·
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cgroup_release_agent · ptrace_traceme · sudoedit_editor · entrybleed
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(KASLR leak primitive) · refluxfs (CVE-2026-64600, `--full-chain`:
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`/etc/passwd` root pop on a private-extent XFS target)
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**🟡 Modules with opt-in `--full-chain`:**
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af_packet · af_packet2 · af_unix_gc · cls_route4 · fuse_legacy ·
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nf_tables · nft_set_uaf · nft_fwd_dup · nft_payload ·
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netfilter_xtcompat · stackrot · sudo_samedit · sequoia · vmwgfx
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### Empirical verification (29 of 41 CVEs)
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Records in [`docs/VERIFICATIONS.jsonl`](docs/VERIFICATIONS.jsonl) prove
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each verdict against a known-target VM. Coverage:
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| Distro / kernel | Modules verified |
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|---|---|
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| Ubuntu 18.04 (4.15.0, sudo 1.8.21p2) | af_packet · ptrace_traceme · sudo_samedit · sudo_runas_neg1 |
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| Ubuntu 20.04 (5.4.0-26 pinned + 5.15 HWE) | af_packet2 · cls_route4 · nft_payload · overlayfs · pwnkit · sequoia · tioscpgrp |
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| Ubuntu 22.04 (5.15 stock + mainline 5.15.5 / 6.1.10 / 6.19.7) | af_unix_gc · dirty_pipe · dirtydecrypt · entrybleed · nf_tables · nft_set_uaf · nft_pipapo · overlayfs_setuid · stackrot · sudoedit_editor · sudo_chwoot |
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| Debian 11 (5.10 stock) | cgroup_release_agent · fuse_legacy · netfilter_xtcompat · nft_fwd_dup |
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| Debian 12 (6.1 stock + udisks2 / polkit allow rule) | pack2theroot · udisks_libblockdev |
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| Rocky Linux 9.8 (5.14.0-687.10.1.el9_8.0.1, stock XFS + `reflink=1`) | refluxfs |
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**Not yet verified (12):** `vmwgfx` (VMware-guest-only — no public Vagrant
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box), `dirty_cow` (needs ≤ 4.4 kernel — older than every supported box),
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`mutagen_astronomy` (mainline 4.14.70 kernel-panics on Ubuntu 18.04
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rootfs — needs CentOS 6 / Debian 7), `pintheft` & `vsock_uaf` (kernel
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modules not loaded on common Vagrant boxes), `fragnesia` (mainline 7.0.5
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kernel .debs depend on the t64-transition libs from Ubuntu 24.04+/Debian
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13+; no Parallels-supported box has those yet), `ptrace_pidfd` (brand-new
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2026-05 Qualys disclosure — added this cycle, VM sweep pending), `sudo_host`
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(brand-new 2025-06 Stratascale disclosure — added this cycle, VM sweep
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pending), `cifswitch` (detect + `add_key` primitive VM-verified; full chain
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+ patched-kernel discriminator pending), `nft_catchall` (reconstructed
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kernel-UAF trigger, not VM-verified), `bad_epoll` (reconstructed epoll
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race trigger — deliberately under-driven, not VM-verified), `ghostlock`
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(reconstructed rtmutex/futex-PI stack-UAF trigger — deliberately
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under-driven, not VM-verified). All twelve are
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flagged in
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[`tools/verify-vm/targets.yaml`](tools/verify-vm/targets.yaml) with rationale.
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See [`CVES.md`](CVES.md) for per-module CVE, kernel range, and
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detection status. Run `skeletonkey --module-info <name>` for the
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embedded verification records per module.
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## Quickstart
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```bash
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# Install (x86_64 / arm64; checksum-verified)
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curl -sSL https://github.com/KaraZajac/SKELETONKEY/releases/latest/download/install.sh | sh
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# What's this box vulnerable to? (no sudo)
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skeletonkey --scan
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# One-page operator briefing for a single CVE: CWE / MITRE ATT&CK /
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# CISA KEV status, live detect() trace, OPSEC footprint, detection
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# coverage. Useful for triage tickets and SOC analyst handoffs.
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skeletonkey --explain nf_tables
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# Pick the safest LPE and run it
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skeletonkey --auto --i-know
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# Deploy detection rules (needs sudo to write into /etc/audit/rules.d/)
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skeletonkey --detect-rules --format=auditd \
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| sudo tee /etc/audit/rules.d/99-skeletonkey.rules
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# Fleet scan — many hosts via SSH, aggregated JSON for SIEM
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./tools/skeletonkey-fleet-scan.sh --binary skeletonkey \
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--ssh-key ~/.ssh/id_rsa hosts.txt
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```
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**SKELETONKEY runs as a normal unprivileged user** — that's the point.
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`--scan`, `--audit`, `--exploit`, and `--detect-rules` all work without
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`sudo`. Only `--mitigate` and rule-file installation write root-owned
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paths.
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### Example: unprivileged → root
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```text
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$ id
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uid=1000(kara) gid=1000(kara) groups=1000(kara)
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$ skeletonkey --auto --i-know
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[*] auto: host=demo distro=ubuntu/24.04 kernel=5.15.0-56-generic arch=x86_64
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[*] auto: active probes enabled — brief /tmp file touches and fork-isolated namespace probes
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[*] auto: scanning 45 modules for vulnerabilities...
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[+] auto: dirty_pipe VULNERABLE (safety rank 90)
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[+] auto: cgroup_release_agent VULNERABLE (safety rank 98)
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[+] auto: pwnkit VULNERABLE (safety rank 100)
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[ ] auto: copy_fail patched or not applicable
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[ ] auto: nf_tables precondition not met
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...
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[*] auto: scan summary — 3 vulnerable, 21 patched/n.a., 7 precondition-fail, 0 indeterminate
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[*] auto: 3 vulnerable modules found. Safest is 'pwnkit' (rank 100).
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[*] auto: launching --exploit pwnkit...
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[+] pwnkit: writing gconv-modules cache + payload.so...
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[+] pwnkit: execve(pkexec) with NULL argv + crafted envp...
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# id
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uid=0(root) gid=0(root) groups=0(root)
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```
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The safety ranking goes: **structural escapes** (no kernel state
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touched) → **page-cache writes** → **userspace cred-races** →
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**kernel primitives** → **kernel races** (least predictable). The
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goal is to never crash a production box looking for root.
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## How it works
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Each CVE (or tightly-related family) is a **module** under `modules/`.
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Modules export a standard interface (`detect / exploit / mitigate /
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cleanup`) plus metadata (kernel range, detection rule text). The
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top-level binary dispatches per command:
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- `--scan` walks every module's `detect()` against the running host
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- `--exploit <name> --i-know` runs the named module's exploit (the
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`--i-know` flag is the authorization gate)
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- `--auto --i-know` does the scan, ranks by safety, runs the safest
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- `--detect-rules --format=<auditd|sigma|yara|falco>` emits the
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embedded rule corpus
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- `--mitigate <name>` / `--cleanup <name>` apply / undo temporary
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mitigations (module-dependent — most kernel modules say "upgrade")
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- `--dump-offsets` reads `/proc/kallsyms` + `/boot/System.map` and
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emits a ready-to-paste C entry for the `--full-chain` offset table
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See [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) for the
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module-loader design.
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## The verified-vs-claimed bar
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Most public PoC repos hardcode offsets for one kernel build and
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silently break elsewhere. SKELETONKEY refuses to ship fabricated
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offsets. The shared `--full-chain` finisher only returns
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`EXPLOIT_OK` after a setuid bash sentinel file *actually appears*;
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otherwise modules return `EXPLOIT_FAIL` with a diagnostic. Operators
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populate the offset table once per target kernel via
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`skeletonkey --dump-offsets` and either set env vars or upstream the
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entry via PR ([`CONTRIBUTING.md`](CONTRIBUTING.md)).
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## Build from source
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```bash
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git clone https://github.com/KaraZajac/SKELETONKEY.git
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cd SKELETONKEY
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make
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./skeletonkey --version
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```
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Builds clean with gcc or clang on any modern Linux. macOS dev builds
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also compile (modules with Linux-only headers stub out gracefully).
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## Status
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**v0.9.14 cut 2026-07-23.** 46 modules across 41 CVEs — **every
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year 2016 → 2026 now covered**. Newest: `refluxfs` (CVE-2026-64600,
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Qualys TRU's "RefluXFS" — a nine-year TOCTOU race in the XFS **reflink
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copy-on-write** path: `xfs_reflink_fill_cow_hole()` drops `ILOCK` to wait
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for transaction log space, then re-checks the refcount btree at a
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**stale** physical block without re-reading the data fork, so a
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direct-I/O writer treats a still-shared block as private and writes to it
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in place. The primitive is an arbitrary overwrite of the **on-disk
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contents of any readable file** — data, not memory corruption — so there
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are **no offsets, no ROP, no KASLR/SMEP/SMAP** to defeat, and SELinux
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enforcing, containers and seccomp are all irrelevant. Because the
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victim's inode is never written, its `mtime`/`ctime`/size never change
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and **file-integrity monitoring cannot see it**. Unprivileged, no userns,
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no crafted image — reachable wherever an XFS volume is mounted
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`reflink=1`, the installer default on RHEL/CentOS/Rocky/Alma/Oracle 8-10,
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Fedora Server ≥ 31 and Amazon Linux 2023. **🟢 VM-verified full chain**:
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`--exploit refluxfs --i-know --full-chain` reflink-clones `/etc/passwd`,
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races the CoW window, strips root's password on-disk and returns
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`EXPLOIT_OK` (`su root`, empty password → uid 0) — confirmed on Rocky 9.8,
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every other account preserved, backed up + restorable. One caveat found
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in testing: the target's extent must be **private** going in (an
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already-shared file isn't attackable; normal `useradd`/`passwd` churn
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makes it private). Plain `--exploit` runs only a safe own-files trigger),
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`ghostlock` (CVE-2026-43499,
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VEGA / Nebula Security's "GhostLock" — a ~15-year rtmutex/futex requeue-PI
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use-after-free on **kernel stack** memory where `remove_waiter()` clears
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`pi_blocked_on` on the wrong task during the `-EDEADLK` deadlock-rollback,
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raced by a sibling-CPU `sched_setattr()` priority walk; reachable by **any
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unprivileged user with no user namespace**; VEGA / Nebula kernelCTF public
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PoC ($92k, ~97% stable) — shipped as a deliberately under-driven,
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reconstructed trigger anchored on a safe `-EDEADLK` reachability witness
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with the corpus's lowest `--auto` safety rank), `bad_epoll` (CVE-2026-46242,
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Jaeyoung Chung's "Bad Epoll" — a race UAF in `fs/eventpoll.c` reachable by
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any unprivileged user with no user namespace; kernelCTF public PoC),
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`nft_catchall` (CVE-2026-23111, the nf_tables `nft_map_catchall_activate`
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abort-path UAF — an inverted condition frees a chain still referenced by a
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catch-all GOTO map element; public reproduction by FuzzingLabs), and
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`cifswitch` (CVE-2026-46243, Asim Manizada's "CIFSwitch" — the
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`cifs.spnego` key type trusts userspace-forged authority fields, coercing
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the root `cifs.upcall` helper into loading an attacker NSS module as root).
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v0.9.0 added 5 gap-fillers
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(`mutagen_astronomy` / `sudo_runas_neg1` / `tioscpgrp` / `vsock_uaf` /
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`nft_pipapo`); v0.8.0 added 3 (`sudo_chwoot` / `udisks_libblockdev` /
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`pintheft`). v0.9.1 and v0.9.2 are verification-only sweeps that took
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the verified count from 22 → 28 by booting real vulnerable kernels
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(Ubuntu mainline 5.4.0-26, 5.15.5, 6.19.7 + provisioner-built sudo
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1.9.16p1 + Debian 12 + polkit allow rule for udisks).
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**29 empirically verified** against real Linux VMs (Ubuntu 18.04 /
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20.04 / 22.04 + Debian 11 / 12 + Rocky Linux 9.8 + mainline kernels
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from kernel.ubuntu.com). 88-test unit harness + ASan/UBSan + clang-tidy on
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every push. 4 prebuilt binaries (x86_64 + arm64, each in dynamic +
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static-musl flavors).
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Reliability + accuracy work in v0.7.x:
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- Shared **host fingerprint** (`core/host.{h,c}`) populated once at
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startup — kernel/distro/userns gates/sudo+polkit versions — exposed
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to every module via `ctx->host`.
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- **Test harness** (`tests/`, `make test`) — 88 tests: 33 kernel_range
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unit tests + 55 detect() integration tests over mocked host
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fingerprints. Runs in CI on every push.
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- **VM verifier** (`tools/verify-vm/`) — Vagrant + Parallels scaffold
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that boots known-vulnerable kernels (stock distro + mainline via
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kernel.ubuntu.com), runs `--explain --active` per module, records
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match/MISMATCH/PRECOND_FAIL as JSON. 29 modules confirmed end-to-end.
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- **`--explain <module>`** — single-page operator briefing: CVE / CWE
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/ MITRE ATT&CK / CISA KEV status, host fingerprint, live detect()
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trace, OPSEC footprint, detection-rule coverage, verified-on
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records. Paste-into-ticket ready.
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- **CVE metadata pipeline** (`tools/refresh-cve-metadata.py`) — fetches
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CISA KEV catalog + NVD CWE; 13 of 40 modules cover KEV-listed CVEs.
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- **151 detection rules** across auditd / sigma / yara / falco; one
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command exports the corpus to your SIEM.
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- `--auto` upgrades: per-detect 15s timeout, fork-isolated detect +
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exploit, structured verdict table, scan summary, `--dry-run`.
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Not yet verified (12 of 41 CVEs): `vmwgfx` (VMware-guest only),
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`dirty_cow` (needs ≤ 4.4 kernel), `mutagen_astronomy` (mainline
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4.14.70 panics on Ubuntu 18.04 rootfs — needs CentOS 6 / Debian 7),
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`pintheft` + `vsock_uaf` (kernel modules not autoloaded on common
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Vagrant boxes), `fragnesia` (mainline 7.0.5 .debs need t64-transition
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libs from Ubuntu 24.04+ / Debian 13+), `ptrace_pidfd` + `sudo_host`
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+ `cifswitch` (cifswitch detect + primitive VM-verified; full chain
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pending) + `nft_catchall` (reconstructed kernel-UAF trigger, not
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VM-verified) + `bad_epoll` (reconstructed epoll race trigger,
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deliberately under-driven, not VM-verified) + `ghostlock` (reconstructed
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rtmutex/futex-PI stack-UAF trigger, deliberately under-driven, not
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VM-verified). Rationale in
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[`tools/verify-vm/targets.yaml`](tools/verify-vm/targets.yaml).
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See [`ROADMAP.md`](ROADMAP.md) for the next planned modules and
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infrastructure work.
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## Contributing
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PRs welcome for: kernel offsets (run `--dump-offsets` on a target
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kernel, paste into `core/offsets.c`), new modules, detection rules,
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and CVE-status corrections. See [`CONTRIBUTING.md`](CONTRIBUTING.md).
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**Keeping `kernel_range` tables current.** `tools/refresh-kernel-ranges.py`
|
||
polls Debian's security tracker and reports drift between each
|
||
module's hardcoded `kernel_patched_from` thresholds and the
|
||
fixed-versions Debian actually ships. Run periodically (or in CI)
|
||
to catch new backports that need to land in the corpus:
|
||
|
||
```bash
|
||
tools/refresh-kernel-ranges.py # human report
|
||
tools/refresh-kernel-ranges.py --json # machine-readable
|
||
tools/refresh-kernel-ranges.py --patch # proposed C-source edits
|
||
```
|
||
|
||
## Acknowledgments
|
||
|
||
Each module credits the original CVE reporter and PoC author in its
|
||
`NOTICE.md`. SKELETONKEY is the bundling and bookkeeping layer;
|
||
the research credit belongs to the people who found the bugs.
|
||
|
||
## License
|
||
|
||
MIT — see [`LICENSE`](LICENSE).
|