CVE-2026-63827

CVE CVE-2026-63827EUVD EUVD-2026-45493Published 2026-07-19T12:02:22.000ZLast changed 2026-08-05T12:36:10.000ZCVSS 7.8

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix use-after-free in rawdata dedup loop aa_replace_profiles() walks ns->rawdata_list to dedup the incoming policy blob against entries already attached to existing profiles. Per the kernel-doc on struct aa_loaddata, list membership does not hold a reference: profiles hold pcount, and when the last pcount drops, do_ploaddata_rmfs() is queued on a workqueue that takes ns->lock and removes the entry. Between dropping the last pcount and the workqueue running, an entry remains on the list with pcount == 0. aa_get_profile_loaddata() is an unconditional kref_get() on pcount, so when the dedup loop hits such an entry, refcount hardening reports refcount_t: addition on 0; use-after-free. inside aa_replace_profiles(), and the poisoned counter then trips "saturated" and "underflow" warnings on the subsequent uses of the same loaddata. Before commit a0b7091c4de4 ("apparmor: fix race on rawdata dereference") the dedup path used a get_unless_zero-style helper on a single counter, so the existing "if (tmp)" guard was meaningful. The split-refcount refactor introduced aa_get_profile_loaddata(), which has plain kref_get() semantics, and the guard quietly became a no-op. Introduce aa_get_profile_loaddata_not0(), matching the existing _not0 convention used by aa_get_profile_not0(), and use it for the rawdata_list dedup lookup so dying entries are skipped. Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu 24.04 + stress-ng 0.17.06: stress-ng --apparmor 1 --klog-check --timeout 60s Without this patch the three refcount_t warnings fire within a few seconds. With it the same 60 s run is clean. Coverage is a smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN and CONFIG_PROVE_LOCKING would be welcome from anyone with the cycles.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux patch: 6.6.144; patch: 6.18.38; 7.0; patch: 7.2-rc1; 6.19.8 <6.20; 5.10.253 <5.10.261; patch: 5.15.212; f9761add6d100962a23996cb68f3d6abdd4d1815 <ce261a20b41db522e320a41bbf1292bf85af66df; 6ef1f2926c41ab96952d9696d55a052f1b3a9418 <15fd83a1e42ede15070968806bb6c8b1a5170688; 6b6ba87579c7e7c669e0bec91823e7fb693bc5df <a7a2890028f16e5b0af0bb005d80fcb32559cca3; a0b7091c4de45a7325c8780e6934a894f92ac86b <6f060496d03e4dc560a40f73770bd08335cb7a27; patch: 0; 5.15.203 <5.15.212; patch: 6.1.177; 6.1.169 <6.1.177; patch: 5.10.261; a0b7091c4de45a7325c8780e6934a894f92ac86b <5e34fa9f6f7cd688ae153fff13139a5cf2d42339; af782cc8871e3683ddd5a3cd2f7df526599863a9 <c3ca2631073b2cef06824fd2bfc452ff7a1023de; 6.18.18 <6.18.38; 6.12.77 <6.12.95; patch: 6.12.95; patch: 7.1.3; 763e838adc3c7ec5a7df2990ce84cad951e42721; d9d8560b9b7932f8cffc4c068c14289220900f79 <b17f0c59cc1525765625cf07d0391b7f9c1ed7e5; 3b8e77c7abab40e6de9ad9de730d77984a498840 <643221da57dbb1a8fd800610331cf1ec27969f71; 6.6.130 <6.6.144

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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