Verified 2026-06-08 on Ubuntu 24.04.4 / kernel 6.8.0-117-generic under
QEMU/HVF (offline: cloud image + payload iso, no guest networking):
- modprobe cifs registers the cifs.spnego key type (cifs-utils not needed
to reach the primitive).
- Independent python3 ctypes add_key('cifs.spnego', forged
uid/creduid/upcall_target) ACCEPTED (user-key control also accepted);
module exploit() independently reported 'primitive CONFIRMED' then the
honest EXPLOIT_FAIL.
- detect() returned PRECOND_FAIL without cifs-utils and VULNERABLE under
SKELETONKEY_CIFS_ASSUME_PRESENT=1.
Still pending (so cifswitch stays 🟡 and is NOT counted as a verified
end-to-end CVE; verified count stays 28 of 37): a patched kernel
(>=6.12.90/7.0.10) to prove add_key is REJECTED there (probe discriminates
fixed-from-vulnerable), and the full namespace+NSS root-pop. Recorded in
NOTICE.md, CVES.md, RELEASE_NOTES.md, and tools/verify-vm/targets.yaml.
CIFSwitch is the newest kernel-7-era LPE not already in the corpus: a
~19-year-old logic flaw in fs/smb/client/cifs_spnego.c where the
cifs.spnego request-key type accepts key descriptions created by
userspace (add_key(2)/request_key(2)) without verifying the request came
from the in-kernel CIFS client. The description's authority-bearing
fields (pid/uid/creduid/upcall_target) are trusted by the root cifs.upcall
helper; with user+mount namespace tricks an unprivileged user coerces
cifs.upcall into loading an attacker NSS module as root. Fixed upstream by
3da1fdf4efbc (merged 7.1-rc5); CWE-20; not in CISA KEV.
Takes the corpus to 42 modules / 37 CVEs.
🟡 honest port — full chain not VM-verified. detect() gates on the kernel
version (Debian backports 5.10.257/6.1.174/6.12.90/7.0.10) AND on the
cifs userspace path (cifs.upcall / cifs.spnego request-key rule), so a
vulnerable kernel without cifs-utils is PRECOND_FAIL not a false positive
(override via SKELETONKEY_CIFS_ASSUME_PRESENT=1/0). exploit() fires only
the non-destructive add_key(2) cifs.spnego probe (no upcall, loads
nothing, revoked immediately) and returns EXPLOIT_FAIL without a euid-0
witness — the namespace+NSS root-pop is not bundled until VM-verified.
--mitigate blocklists the cifs module; --cleanup reverts.
Wired everywhere: registry, Makefile, safety rank (86), 6 detect() test
rows (env-driven precondition override), CVE_METADATA.json + cve_metadata.c
+ KEV_CROSSREF.md (sorted insert, CWE-20/T1068/not-KEV), README + CVES.md
+ website counts (42/37) and a yellow module pill, RELEASE_NOTES v0.9.10,
verify-vm target (sweep pending). Credit: Asim Manizada. Version 0.9.10.
KaraZajac