CVE-2026-53390
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix out-of-bounds read in smb_check_perm_dacl()
The permission-check ACE walk in smb_check_perm_dacl() validates the ACE header size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it never checks that ace->size is actually large enough to contain num_subauth sub-authorities before compare_sids() dereferences them.
CIFS_SID_BASE_SIZE covers the SID header up to but excluding the sub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header, so the existing guards only guarantee the 8-byte SID base, i.e. zero sub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for i < min(local_sid->num_subauth, ace->sid.num_subauth).
Leer descripción completaMostrar menos
The local comparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid() result) always have at least one sub-authority, and an attacker controls the ACE revision and authority bytes (which lie within the in-bounds SID base), so they can match one of those SIDs and force the sub_auth read.
A crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of the security descriptor therefore causes a heap out-of-bounds read of up to SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd allocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr() into a buffer sized exactly to the on-disk data (kzalloc(sd_size) in ndr_decode_v4_ntacl()), so the read lands past the allocation. The malformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL is not normalised before being written to the security.NTACL xattr) and the read fires on a subsequent SMB2_CREATE access check, making this reachable by an authenticated client on a share that uses ACL xattrs.
Add the missing num_subauth-versus-ace_size check, mirroring the identical guards already present in the sibling parsers parse_dacl() and smb_inherit_dacl().
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Puntuación base: 8.1
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.47%
- Percentil entre todas las CVEs puntuadas: 38
- Fecha de la puntuación: 4/10/2026
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
T1210Exploitation of Remote Serviceslateral movement85 % - Impacto principal
T1005Data from Local Systemcollection90 %
Vulnerabilidad de lectura fuera de límites (CWE-125) en kernel Linux, acceso remoto (AV:N) requiriendo autenticación (PR:L). El atacante lee memoria del kernel via SMB2_CREATE access check en servidor ksmbd. Confidencialidad Alta (C:H).
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)
CWE
- CWE-125
Referencias
- https://git.kernel.org/stable/c/1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b
- https://git.kernel.org/stable/c/36599894fa8536fefdf1e296c0af71b8b7226859
- https://git.kernel.org/stable/c/7627ff8c4f9919f14de562b0160ab4ec9d80b1f7
- https://git.kernel.org/stable/c/988c93d3bba066d8669143e6ec30bb2be9608d53
- https://git.kernel.org/stable/c/c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0
- https://git.kernel.org/stable/c/d5c81a095c86fe507c032d08f3a8cfc518444927
- https://git.kernel.org/stable/c/e36e35660adb9b8ef1435ac359151dda5f094c55
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-53390",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 8.1,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.2,
"exploitabilityScore": 2.8
}
]
},
"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": "282cbbb476b9f35793452bc461934af4c7eca169",
"lessThan": "c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0",
"versionType": "git"
},
{
"status": "affected",
"version": "f20adc4ef7428bc485ee83fd1a592252fb87718b",
"lessThan": "988c93d3bba066d8669143e6ec30bb2be9608d53",
"versionType": "git"
},
{
"status": "affected",
"version": "325d4ac11f526cb8964cff14548ccf02d8c756d8",
"lessThan": "36599894fa8536fefdf1e296c0af71b8b7226859",
"versionType": "git"
},
{
"status": "affected",
"version": "95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c",
"lessThan": "d5c81a095c86fe507c032d08f3a8cfc518444927",
"versionType": "git"
},
{
"status": "affected",
"version": "90089584b2e25c4510b7b987387b4405f0673ece",
"lessThan": "7627ff8c4f9919f14de562b0160ab4ec9d80b1f7",
"versionType": "git"
},
{
"status": "affected",
"version": "d07b26f39246a82399661936dd0c853983cfade7",
"lessThan": "e36e35660adb9b8ef1435ac359151dda5f094c55",
"versionType": "git"
},
{
"status": "affected",
"version": "d07b26f39246a82399661936dd0c853983cfade7",
"lessThan": "1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b",
"versionType": "git"
},
{
"status": "affected",
"version": "151b1799861fde38087c08f613abc2843ef597b0",
"versionType": "git"
},
{
"status": "affected",
"version": "5.15.210",
"lessThan": "5.15.212",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.1.176",
"lessThan": "6.1.177",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.140",
"lessThan": "6.6.144",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.12.84",
"lessThan": "6.12.95",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.18.25",
"lessThan": "6.18.38",
"versionType": "semver"
},
{
"status": "affected",
"version": "7.0.2",
"lessThan": "7.1",
"versionType": "semver"
}
],
"programFiles": [
"fs/smb/server/smbacl.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.1"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.1",
"versionType": "semver"
},
{
"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": [
"fs/smb/server/smbacl.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-07-19T12:16:50.000",
"references": [
{
"url": "https://git.kernel.org/stable/c/1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/36599894fa8536fefdf1e296c0af71b8b7226859",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7627ff8c4f9919f14de562b0160ab4ec9d80b1f7",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/988c93d3bba066d8669143e6ec30bb2be9608d53",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d5c81a095c86fe507c032d08f3a8cfc518444927",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/e36e35660adb9b8ef1435ac359151dda5f094c55",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Analyzed",
"weaknesses": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"description": [
{
"lang": "en",
"value": "CWE-125"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix out-of-bounds read in smb_check_perm_dacl()\n\nThe permission-check ACE walk in smb_check_perm_dacl() validates the ACE\nheader size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it\nnever checks that ace->size is actually large enough to contain\nnum_subauth sub-authorities before compare_sids() dereferences them.\n\nCIFS_SID_BASE_SIZE covers the SID header up to but excluding the\nsub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header,\nso the existing guards only guarantee the 8-byte SID base, i.e. zero\nsub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for\ni < min(local_sid->num_subauth, ace->sid.num_subauth). The local\ncomparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid()\nresult) always have at least one sub-authority, and an attacker controls\nthe ACE revision and authority bytes (which lie within the in-bounds SID\nbase), so they can match one of those SIDs and force the sub_auth read.\n\nA crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of\nthe security descriptor therefore causes a heap out-of-bounds read of up\nto SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd\nallocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr()\ninto a buffer sized exactly to the on-disk data (kzalloc(sd_size) in\nndr_decode_v4_ntacl()), so the read lands past the allocation. The\nmalformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL\nis not normalised before being written to the security.NTACL xattr) and\nthe read fires on a subsequent SMB2_CREATE access check, making this\nreachable by an authenticated client on a share that uses ACL xattrs.\n\nAdd the missing num_subauth-versus-ace_size check, mirroring the\nidentical guards already present in the sibling parsers parse_dacl() and\nsmb_inherit_dacl()."
}
],
"lastModified": "2026-08-17T05:17:13.293",
"configurations": [
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "42434AE1-4361-420E-AC94-62114ADF9A54",
"versionEndExcluding": "5.15.212",
"versionStartIncluding": "5.15.210"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "86F30E4E-AC0B-4F7E-BD0D-8B4DFF40C8E5",
"versionEndExcluding": "6.6.144",
"versionStartIncluding": "6.6.140"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "18BFBAB5-F8BE-445D-A4DC-A598E4DD65C3",
"versionEndExcluding": "6.12.95",
"versionStartIncluding": "6.12.84"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "54268F52-8016-498C-94D4-7A78B8F35FEC",
"versionEndExcluding": "6.18.38",
"versionStartIncluding": "6.18.25"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "BF755E4C-E134-4585-AFB9-61E683441DD9",
"versionEndExcluding": "7.1.3",
"versionStartIncluding": "7.0.2"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.1.176:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "31ED607F-61AA-41F2-B79C-959EDFA61657"
}
],
"operator": "OR"
}
]
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}