{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63827", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.014Z", "datePublished": "2026-07-19T12:02:22.083Z", "dateUpdated": "2026-08-17T04:51:35.761Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:51:35.761Z" }, "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." } ], "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "security/apparmor/include/policy_unpack.h", "security/apparmor/policy.c" ], "versions": [ { "version": "3b8e77c7abab40e6de9ad9de730d77984a498840", "lessThan": "643221da57dbb1a8fd800610331cf1ec27969f71", "status": "affected", "versionType": "git" }, { "version": "d9d8560b9b7932f8cffc4c068c14289220900f79", "lessThan": "b17f0c59cc1525765625cf07d0391b7f9c1ed7e5", "status": "affected", "versionType": "git" }, { "version": "6b6ba87579c7e7c669e0bec91823e7fb693bc5df", "lessThan": "a7a2890028f16e5b0af0bb005d80fcb32559cca3", "status": "affected", "versionType": "git" }, { "version": "6ef1f2926c41ab96952d9696d55a052f1b3a9418", "lessThan": "15fd83a1e42ede15070968806bb6c8b1a5170688", "status": "affected", "versionType": "git" }, { "version": "f9761add6d100962a23996cb68f3d6abdd4d1815", "lessThan": "ce261a20b41db522e320a41bbf1292bf85af66df", "status": "affected", "versionType": "git" }, { "version": "af782cc8871e3683ddd5a3cd2f7df526599863a9", "lessThan": "c3ca2631073b2cef06824fd2bfc452ff7a1023de", "status": "affected", "versionType": "git" }, { "version": "a0b7091c4de45a7325c8780e6934a894f92ac86b", "lessThan": "5e34fa9f6f7cd688ae153fff13139a5cf2d42339", "status": "affected", "versionType": "git" }, { "version": "a0b7091c4de45a7325c8780e6934a894f92ac86b", "lessThan": "6f060496d03e4dc560a40f73770bd08335cb7a27", "status": "affected", "versionType": "git" }, { "version": "763e838adc3c7ec5a7df2990ce84cad951e42721", "status": "affected", "versionType": "git" }, { "version": "5.10.253", "lessThan": "5.10.261", "status": "affected", "versionType": "semver" }, { "version": "5.15.203", "lessThan": "5.15.212", "status": "affected", "versionType": "semver" }, { "version": "6.1.169", "lessThan": "6.1.177", "status": "affected", "versionType": "semver" }, { "version": "6.6.130", "lessThan": "6.6.144", "status": "affected", "versionType": "semver" }, { "version": "6.12.77", "lessThan": "6.12.95", "status": "affected", "versionType": "semver" }, { "version": "6.18.18", "lessThan": "6.18.38", "status": "affected", "versionType": "semver" }, { "version": "6.19.8", "lessThan": "6.20", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "security/apparmor/include/policy_unpack.h", "security/apparmor/policy.c" ], "versions": [ { "version": "7.0", "status": "affected" }, { "version": "0", "lessThan": "7.0", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.177", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.144", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.38", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.3", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "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" } ] } ] } ], "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" } ], "title": "apparmor: fix use-after-free in rawdata dedup loop", "x_generator": { "engine": "bippy-1.2.0" } } } }