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smb: client: fix heap overflow in DACL owner/group rewrite

Type: advisorySource: Official CVE List1 source record

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)

Announced Source revision 1
Original source ↗

CVE-2026-97555

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-97555

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "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"
      }
    ],
    "programFiles": [
      "fs/smb/client/cifsacl.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.12"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.12",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.158",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.111",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.53",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.7",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/smb/client/cifsacl.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-97555

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#38007 · Revision 1
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