{"id":"CVE-2026-63827","state":"PUBLISHED","title":"apparmor: fix use-after-free in rawdata dedup loop","description":"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 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.","publishedAt":"2026-07-19T12:02:22.083Z","updatedAt":"2026-08-17T04:51:35.761Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3b8e77c7abab40e6de9ad9de730d77984a498840","status":"affected","lessThan":"643221da57dbb1a8fd800610331cf1ec27969f71","versionType":"git"},{"version":"d9d8560b9b7932f8cffc4c068c14289220900f79","status":"affected","lessThan":"b17f0c59cc1525765625cf07d0391b7f9c1ed7e5","versionType":"git"},{"version":"6b6ba87579c7e7c669e0bec91823e7fb693bc5df","status":"affected","lessThan":"a7a2890028f16e5b0af0bb005d80fcb32559cca3","versionType":"git"},{"version":"6ef1f2926c41ab96952d9696d55a052f1b3a9418","status":"affected","lessThan":"15fd83a1e42ede15070968806bb6c8b1a5170688","versionType":"git"},{"version":"f9761add6d100962a23996cb68f3d6abdd4d1815","status":"affected","lessThan":"ce261a20b41db522e320a41bbf1292bf85af66df","versionType":"git"},{"version":"af782cc8871e3683ddd5a3cd2f7df526599863a9","status":"affected","lessThan":"c3ca2631073b2cef06824fd2bfc452ff7a1023de","versionType":"git"},{"version":"a0b7091c4de45a7325c8780e6934a894f92ac86b","status":"affected","lessThan":"5e34fa9f6f7cd688ae153fff13139a5cf2d42339","versionType":"git"},{"version":"a0b7091c4de45a7325c8780e6934a894f92ac86b","status":"affected","lessThan":"6f060496d03e4dc560a40f73770bd08335cb7a27","versionType":"git"},{"version":"763e838adc3c7ec5a7df2990ce84cad951e42721","status":"affected","versionType":"git"},{"version":"5.10.253","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.203","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"6.1.169","status":"affected","lessThan":"6.1.177","versionType":"semver"},{"version":"6.6.130","status":"affected","lessThan":"6.6.144","versionType":"semver"},{"version":"6.12.77","status":"affected","lessThan":"6.12.95","versionType":"semver"},{"version":"6.18.18","status":"affected","lessThan":"6.18.38","versionType":"semver"},{"version":"6.19.8","status":"affected","lessThan":"6.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["security/apparmor/include/policy_unpack.h","security/apparmor/policy.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.38","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["security/apparmor/include/policy_unpack.h","security/apparmor/policy.c"]}],"references":["https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71","https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5","https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3","https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688","https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df","https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de","https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339","https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63827.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63827","state":"PUBLISHED","datePublished":"2026-07-19T12:02:22.083Z","dateUpdated":"2026-08-17T04:51:35.761Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.014Z"},"containers":{"cna":{"title":"apparmor: fix use-after-free in rawdata dedup loop","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3b8e77c7abab40e6de9ad9de730d77984a498840","status":"affected","lessThan":"643221da57dbb1a8fd800610331cf1ec27969f71","versionType":"git"},{"version":"d9d8560b9b7932f8cffc4c068c14289220900f79","status":"affected","lessThan":"b17f0c59cc1525765625cf07d0391b7f9c1ed7e5","versionType":"git"},{"version":"6b6ba87579c7e7c669e0bec91823e7fb693bc5df","status":"affected","lessThan":"a7a2890028f16e5b0af0bb005d80fcb32559cca3","versionType":"git"},{"version":"6ef1f2926c41ab96952d9696d55a052f1b3a9418","status":"affected","lessThan":"15fd83a1e42ede15070968806bb6c8b1a5170688","versionType":"git"},{"version":"f9761add6d100962a23996cb68f3d6abdd4d1815","status":"affected","lessThan":"ce261a20b41db522e320a41bbf1292bf85af66df","versionType":"git"},{"version":"af782cc8871e3683ddd5a3cd2f7df526599863a9","status":"affected","lessThan":"c3ca2631073b2cef06824fd2bfc452ff7a1023de","versionType":"git"},{"version":"a0b7091c4de45a7325c8780e6934a894f92ac86b","status":"affected","lessThan":"5e34fa9f6f7cd688ae153fff13139a5cf2d42339","versionType":"git"},{"version":"a0b7091c4de45a7325c8780e6934a894f92ac86b","status":"affected","lessThan":"6f060496d03e4dc560a40f73770bd08335cb7a27","versionType":"git"},{"version":"763e838adc3c7ec5a7df2990ce84cad951e42721","status":"affected","versionType":"git"},{"version":"5.10.253","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.203","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"6.1.169","status":"affected","lessThan":"6.1.177","versionType":"semver"},{"version":"6.6.130","status":"affected","lessThan":"6.6.144","versionType":"semver"},{"version":"6.12.77","status":"affected","lessThan":"6.12.95","versionType":"semver"},{"version":"6.18.18","status":"affected","lessThan":"6.18.38","versionType":"semver"},{"version":"6.19.8","status":"affected","lessThan":"6.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["security/apparmor/include/policy_unpack.h","security/apparmor/policy.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.38","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["security/apparmor/include/policy_unpack.h","security/apparmor/policy.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71"},{"url":"https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5"},{"url":"https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3"},{"url":"https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688"},{"url":"https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df"},{"url":"https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de"},{"url":"https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339"},{"url":"https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only via local write() to AppArmor policy management interfaces (.load/.replace) under securityfs/apparmorfs, not through any network-facing protocol.\nAC:L - An attacker with policy-admin capability can reliably win the race by concurrently loading/replacing and removing profiles with identical rawdata blobs, as demonstrated by stress-ng reproducing refcount UAF warnings within seconds.\nPR:L - Triggering aa_replace_profiles() requires CAP_MAC_ADMIN plus policy-view rights; on typical AppArmor deployments (e.g. Ubuntu) namespace-root in an unprivileged user namespace can obtain CAP_MAC_ADMIN via unprivileged_userns_apparmor_policy without init-namespace root.\nUI:N - Exploitation is driven entirely by the attacker's own policy load/replace/remove operations and does not require any action from another user or administrator.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel security boundary, not a cross-VM or cross-security-authority escape.\nC:H - The vulnerability is a use-after-free on aa_loaddata profile refcounts; refcount hardening reports \"addition on 0; use-after-free\" and poisons the counter, creating a path to arbitrary kernel memory disclosure.\nI:H - UAF and refcount saturation/underflow on aa_loaddata enable heap corruption primitives that can be leveraged for arbitrary kernel writes and local privilege escalation.\nA:H - The bug reliably triggers refcount_t UAF warnings and corrupts subsequent refcount operations on the same loaddata, causing kernel instability and potential crash/panic under concurrent policy management."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:51:35.761Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.253","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.203","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.169","versionEndExcluding":"6.1.177"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.130","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.77","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.18","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}