modules: add bad_epoll (CVE-2026-46242, "Bad Epoll" epoll teardown race UAF)

Jaeyoung Chung's kernelCTF "Bad Epoll": a race-condition use-after-free in
fs/eventpoll.c. ep_remove() clears file->f_ep under f_lock but keeps using
the file (hlist_del_rcu + unlock) while a concurrent __fput() frees the
still-referenced struct eventpoll. Reachable by any unprivileged user with
no userns / CONFIG / capability; weaponised via cross-cache to a struct
file, /proc/self/fdinfo arb-read, and ROP. Introduced 58c9b016e128 (6.4),
fixed a6dc643c6931 (7.1-rc1), stable backport 7.0.13. CWE-416; not in KEV.

The corpus's first epoll / VFS-teardown module. Shipped as a reconstructed,
deliberately under-driven trigger on the stackrot / nft_catchall contract:
detect() is a pure version gate (>= 6.4 and below the on-branch fix; no
userns precondition -- epoll needs none); exploit() forks a CPU-pinned
child that exercises the ep_remove-vs-__fput close window a hard-bounded 48
attempts / 2s and returns EXPLOIT_FAIL. It does not grind the race to a
win, does not do the cross-cache reclaim, and does not bundle the fdinfo
R/W + ROP (a won race frees a live struct file and rarely trips KASAN ->
silent-corruption risk).

Wired: registry, Makefile, safety rank (12 -- lowest in the corpus; a
kernel race is the least predictable class), 5 detect() test rows (version
gating), CVE metadata (sorted insert, CWE-416 / T1068 / not-KEV), README +
CVES.md + website counts (44/39), RELEASE_NOTES v0.9.12, and a verify-vm
target (sweep pending). Detection rules are intentionally weak/structural
(epoll ubiquitous, rarely KASAN) -- post-exploitation euid-0 transition,
no yara. Also corrects pre-existing README drift in the "not yet verified"
count (8 -> 11). Not VM-verified, so the verified count stays 28 of 39.
Version 0.9.12. Credit: Jaeyoung Chung (J-jaeyoung).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KUq4DGXSPBmPkAyJ9WnM9n

docs/CVE_METADATA.json

@@ -314,6 +314,15 @@
     "in_kev": false,
     "kev_date_added": ""
   },
+  {
+    "cve": "CVE-2026-46242",
+    "module_dir": "bad_epoll_cve_2026_46242",
+    "cwe": "CWE-416",
+    "attack_technique": "T1068",
+    "attack_subtechnique": null,
+    "in_kev": false,
+    "kev_date_added": ""
+  },
   {
     "cve": "CVE-2026-46243",
     "module_dir": "cifswitch_cve_2026_46243",

docs/KEV_CROSSREF.md

@@ -4,7 +4,7 @@ Which SKELETONKEY modules cover CVEs that CISA has observed exploited
 in the wild per the Known Exploited Vulnerabilities catalog.
 Refreshed via `tools/refresh-cve-metadata.py`.
 
-**13 of 38 modules cover KEV-listed CVEs.**
+**13 of 39 modules cover KEV-listed CVEs.**
 
 ## In KEV (prioritize patching)
 
@@ -54,6 +54,7 @@ and are technically reachable. "Not in KEV" is not the same as
 | CVE-2026-31635 | CWE-130 | `dirtydecrypt_cve_2026_31635` |
 | CVE-2026-41651 | CWE-367 | `pack2theroot_cve_2026_41651` |
 | CVE-2026-43494 | ? | `pintheft_cve_2026_43494` |
+| CVE-2026-46242 | CWE-416 | `bad_epoll_cve_2026_46242` |
 | CVE-2026-46243 | CWE-20 | `cifswitch_cve_2026_46243` |
 | CVE-2026-46300 | CWE-787 | `fragnesia_cve_2026_46300` |
 | CVE-2026-46333 | CWE-269 | `ptrace_pidfd_cve_2026_46333` |

docs/RELEASE_NOTES.md

@@ -1,3 +1,51 @@
+## SKELETONKEY v0.9.12 — new LPE module: bad_epoll (CVE-2026-46242)
+
+Adds **`bad_epoll` — CVE-2026-46242 "Bad Epoll"** (Jaeyoung Chung /
+`J-jaeyoung`, submitted to Google's kernelCTF), taking the corpus to **44
+modules / 39 CVEs** and opening a brand-new subsystem: **epoll /
+`fs/eventpoll.c`**. A race-condition use-after-free on the file-teardown
+path — `ep_remove()` clears `file->f_ep` under `file->f_lock` but keeps
+using the file inside the critical section (`hlist_del_rcu()` +
+`spin_unlock()`), so a concurrent `__fput()` observes the transient NULL,
+skips `eventpoll_release_file()`, and frees a `struct eventpoll` still in
+use. The public exploit weaponises the 8-byte UAF write via a cross-cache
+attack to a `struct file`, arbitrary kernel read through
+`/proc/self/fdinfo`, and a ROP chain — ~99% reliable through a
+~6-instruction window, and reachable by **any unprivileged user with no
+user namespace, no CONFIG, and no capability** (which also means there is
+no unprivileged-userns stopgap — the only fix is to patch). Introduced by
+`58c9b016e128` (Linux 6.4); fixed by `a6dc643c6931` (merged 7.1-rc1),
+stable backport 7.0.13. CWE-416 (race root cause CWE-362); not in CISA
+KEV. Also affects Android.
+
+🟡 **Trigger (reconstructed) — deliberately under-driven, primitive-only,
+not VM-verified.** A *won* race frees a live `struct eventpoll` — real
+memory corruption that rarely trips KASAN, so a completed race can
+silently destabilise a vulnerable host. `detect()` is therefore a pure
+kernel-version gate (vulnerable iff ≥ 6.4 and below the fix on-branch;
+stable backport 7.0.13, 7.1+ inherits; 6.1/5.10 not affected) with **no
+active probe** — there is no safe way to distinguish vulnerable from
+patched without winning the race. `exploit()` forks a CPU-pinned child
+that builds the epoll race pair and exercises the `ep_remove`-vs-`__fput`
+concurrent-close window a **hard-bounded** 48 attempts / 2 s (widened with
+`close(dup())` false-sharing storms), snapshots the eventpoll slab, and
+returns `EXPLOIT_FAIL`; it does not grind the race to a win, does not do
+the cross-cache reclaim, and does not bundle the `fdinfo` arbitrary-read +
+ROP root-pop (per-build offsets refused). It carries the corpus's
+**lowest `--auto` safety rank (12)** — a kernel race that frees a live
+`struct file` is the least predictable class, so `--auto` only reaches for
+it after every safer vulnerable module. Detection is intentionally
+weak/structural (epoll syscalls are ubiquitous and the exploit rarely
+trips KASAN) — the shipped auditd/sigma/falco rules key on the
+post-exploitation euid-0 transition, with no yara; treat this as much as a
+blue-team "your stack is nearly blind to this" teaching case as an
+offensive one. Wired: registry, Makefile, safety rank (12), 5 `detect()`
+test rows (version gating), CVE metadata (CWE-416 / T1068 / not-KEV),
+README + CVES.md + website counts (44/39), RELEASE_NOTES v0.9.12, and a
+verify-vm target (sweep pending). Credits Jaeyoung Chung + the upstream
+fix in `NOTICE.md`. Reconstructed from the public kernelCTF PoC and not
+VM-verified, so the verified count stays 28 of 39.
+
 ## SKELETONKEY v0.9.11 — new LPE module: nft_catchall (CVE-2026-23111)
 
 Adds **`nft_catchall` — CVE-2026-23111**, taking the corpus to **43

docs/index.html

@@ -4,9 +4,9 @@
 <meta charset="UTF-8">
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 <title>SKELETONKEY — Linux LPE corpus, VM-verified, SOC-ready detection</title>
-<meta name="description" content="One binary. 43 Linux privilege-escalation modules from 2016 to 2026. 28 of 38 CVEs empirically verified in real Linux VMs. 13 KEV-listed. 151 detection rules across auditd/sigma/yara/falco. MITRE ATT&CK and CWE annotated. --explain gives operator briefings.">
+<meta name="description" content="One binary. 44 Linux privilege-escalation modules from 2016 to 2026. 28 of 39 CVEs empirically verified in real Linux VMs. 13 KEV-listed. 151 detection rules across auditd/sigma/yara/falco. MITRE ATT&CK and CWE annotated. --explain gives operator briefings.">
 <meta property="og:title" content="SKELETONKEY — Linux LPE corpus, VM-verified">
-<meta property="og:description" content="43 Linux LPE modules; 28 of 38 CVEs empirically verified in real VMs. 151 detection rules. ATT&CK + CWE + KEV annotated.">
+<meta property="og:description" content="44 Linux LPE modules; 28 of 39 CVEs empirically verified in real VMs. 151 detection rules. ATT&CK + CWE + KEV annotated.">
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