CVE-2026-97555

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix heap overflow in DACL owner/group rewrite When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a buffer sized according to the on-disk DACL length reported by dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each ACE with a new owner/group SID obtained from the cifs.idmap upcall. Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities, making each ACE up to 76 bytes (sizeof(struct smb_ace)). If the original DACL contains short SIDs (e.g., 1 sub-authority) while the replacement SIDs are long, the rewritten ACEs overflow the allocation. Fix this by always budgeting for worst-case SID expansion: allocate sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which covers the smb_acl header and room for every ACE at maximum SID size. This replaces the previous split logic that used dacl_ptr->size for cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid mounts: both paths can trigger the same rewrite and need the same headroom. KASAN reports this as: BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs] Write of size 4 at addr ffff8881a5e25374 by task chown/5298 ... The buggy address is located 0 bytes to the right of allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)

Severity

HIGH

CVSS score

8.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-25 11:17:05.963000

Last modified

2026-10-30 13:21:07.520000

View original CVE JSON

{
  "id": "CVE-2026-97555",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-25T11:17:05.963",
  "lastModified": "2026-10-30T13:21:07.520",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix heap overflow in DACL owner/group rewrite\n\nWhen id_mode_to_cifs_acl rewrites an existing DACL, it allocates a\nbuffer sized according to the on-disk DACL length reported by\ndacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each\nACE with a new owner/group SID obtained from the cifs.idmap upcall.\nThose SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,\nmaking each ACE up to 76 bytes (sizeof(struct smb_ace)).\n\nIf the original DACL contains short SIDs (e.g., 1 sub-authority) while\nthe replacement SIDs are long, the rewritten ACEs overflow the\nallocation.\n\nFix this by always budgeting for worst-case SID expansion: allocate\nsizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which\ncovers the smb_acl header and room for every ACE at maximum SID size.\nThis replaces the previous split logic that used dacl_ptr->size for\ncifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid\nmounts: both paths can trigger the same rewrite and need the same\nheadroom.\n\nKASAN reports this as:\n  BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]\n  Write of size 4 at addr ffff8881a5e25374 by task chown/5298\n  ...\n  The buggy address is located 0 bytes to the right of\n   allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)"
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/smb/client/cifsacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "4e78b5ff13214353750b87283ff79f62510f5844",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "63c2fbde15ffc9a0c21adf670c38d028e20fa65c",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "d5cea6766ae1868a51c7d17d77d065b4f55c587f",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "7fa84c9ca690643f429ae2709584a47e74b572c9",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "bc3e9dd9d104ca1b75644eab87b38ce8a924aef4",
              "lessThan": "0ee150794c75bcd0be0e24ff3394f433cbae18cc",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/smb/client/cifsacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "5.12",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "5.12",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.224",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.158",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.111",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.53",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.7",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "REQUIRED",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0ee150794c75bcd0be0e24ff3394f433cbae18cc",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4e78b5ff13214353750b87283ff79f62510f5844",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/63c2fbde15ffc9a0c21adf670c38d028e20fa65c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/7fa84c9ca690643f429ae2709584a47e74b572c9",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d5cea6766ae1868a51c7d17d77d065b4f55c587f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}