CVE-2026-63827
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
Leer descripción completaMostrar menos
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:
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.
Detalles técnicos trazas, registros y código del informe original
refcount_t: addition on 0; use-after-free. stress-ng --apparmor 1 --klog-check --timeout 60s
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.12%
- Percentil entre todas las CVEs puntuadas: 2
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1499.004Application or System Exploitationimpact75 %
Vulnerabilidad local (AV:L/PR:L) en kernel Linux que causa use-after-free con refcount hardening; permite DoS por crash al manipular rawdata_list en AppArmor entre unprivileged user privilege level.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688
- https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339
- https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71
- https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27
- https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3
- https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5
- https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de
- https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-63827",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.8,
"attackVector": "LOCAL",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 1.8
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3b8e77c7abab40e6de9ad9de730d77984a498840",
"lessThan": "643221da57dbb1a8fd800610331cf1ec27969f71",
"versionType": "git"
},
{
"status": "affected",
"version": "d9d8560b9b7932f8cffc4c068c14289220900f79",
"lessThan": "b17f0c59cc1525765625cf07d0391b7f9c1ed7e5",
"versionType": "git"
},
{
"status": "affected",
"version": "6b6ba87579c7e7c669e0bec91823e7fb693bc5df",
"lessThan": "a7a2890028f16e5b0af0bb005d80fcb32559cca3",
"versionType": "git"
},
{
"status": "affected",
"version": "6ef1f2926c41ab96952d9696d55a052f1b3a9418",
"lessThan": "15fd83a1e42ede15070968806bb6c8b1a5170688",
"versionType": "git"
},
{
"status": "affected",
"version": "f9761add6d100962a23996cb68f3d6abdd4d1815",
"lessThan": "ce261a20b41db522e320a41bbf1292bf85af66df",
"versionType": "git"
},
{
"status": "affected",
"version": "af782cc8871e3683ddd5a3cd2f7df526599863a9",
"lessThan": "c3ca2631073b2cef06824fd2bfc452ff7a1023de",
"versionType": "git"
},
{
"status": "affected",
"version": "a0b7091c4de45a7325c8780e6934a894f92ac86b",
"lessThan": "5e34fa9f6f7cd688ae153fff13139a5cf2d42339",
"versionType": "git"
},
{
"status": "affected",
"version": "a0b7091c4de45a7325c8780e6934a894f92ac86b",
"lessThan": "6f060496d03e4dc560a40f73770bd08335cb7a27",
"versionType": "git"
},
{
"status": "affected",
"version": "763e838adc3c7ec5a7df2990ce84cad951e42721",
"versionType": "git"
},
{
"status": "affected",
"version": "5.10.253",
"lessThan": "5.10.261",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.15.203",
"lessThan": "5.15.212",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.1.169",
"lessThan": "6.1.177",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.130",
"lessThan": "6.6.144",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.12.77",
"lessThan": "6.12.95",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.18.18",
"lessThan": "6.18.38",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.19.8",
"lessThan": "6.20",
"versionType": "semver"
}
],
"programFiles": [
"security/apparmor/include/policy_unpack.h",
"security/apparmor/policy.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.261",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.177",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.144",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.95",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"security/apparmor/include/policy_unpack.h",
"security/apparmor/policy.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-07-19T12:16:55.960",
"references": [
{
"url": "https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/643221da57dbb1a8fd800610331cf1ec27969f71",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b17f0c59cc1525765625cf07d0391b7f9c1ed7e5",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Awaiting Analysis",
"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."
}
],
"lastModified": "2026-08-17T05:17:20.337",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}