{"id":"CVE-2026-63827","title":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix use-after-free in rawdata dedup loop\n\naa_replace_profiles() walks ns->rawdata_list to dedup the incoming\npolicy blob against entries already attached to e…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix use-after-free in rawdata dedup loop\n\naa_replace_profiles() walks ns->rawdata_list to dedup the incoming\npolicy blob against entries already attached to e…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","published":"2026-07-19","updated":"2026-08-17","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-63827","references":[{"url":"https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00124,"epssPercentile":0.01812,"ingestedAt":"2026-08-17T05:47:49.988Z","slug":"CVE-2026-63827","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix use-after-free in rawdata dedup loop\n\naa_replace_profiles() walks ns->rawdata_list to dedup the incoming\npolicy blob against entries already attached to existing profiles.\nPer the kernel-doc on struct aa_loaddata, list membership does not\nhold a reference: profiles hold pcount, and when the last pcount\ndrops, do_ploaddata_rmfs() is queued on a workqueue that takes\nns->lock and removes the entry. Between dropping the last pcount\nand the workqueue running, an entry remains on the list with\npcount == 0.\n\naa_get_profile_loaddata() is an unconditional kref_get() on\npcount, so when the dedup loop hits such an entry, refcount\nhardening reports\n\n  refcount_t: addition on 0; use-after-free.\n\ninside aa_replace_profiles(), and the poisoned counter then\ntrips \"saturated\" and \"underflow\" warnings on the subsequent\nuses of the same loaddata.\n\nBefore commit a0b7091c4de4 (\"apparmor: fix race on rawdata\ndereference\") the dedup path used a get_unless_zero-style helper\non a single counter, so the existing \"if (tmp)\" guard was\nmeaningful. The split-refcount refactor introduced\naa_get_profile_loaddata(), which has plain kref_get() semantics,\nand the guard quietly became a no-op.\n\nIntroduce aa_get_profile_loaddata_not0(), matching the existing\n_not0 convention used by aa_get_profile_not0(), and use it for\nthe rawdata_list dedup lookup so dying entries are skipped.\n\nReproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu\n24.04 + stress-ng 0.17.06:\n\n  stress-ng --apparmor 1 --klog-check --timeout 60s\n\nWithout this patch the three refcount_t warnings fire within a\nfew seconds. With it the same 60 s run is clean. Coverage is a\nsmoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN\nand CONFIG_PROVE_LOCKING would be welcome from anyone with the\ncycles.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}