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VulnerabilityPublished Updated

CVE-2026-97555: Linux kernel · smb: client: fix heap overflow in DACL owner/group rewrite

Source GCVE Database

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Authoritative record:CVE-2026-97555· High 8.8

Not known to be exploited · CVSS 8.8 High · fixed in fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1 : patch Linux kernel soon.

Data as of 30 Oct 2026, 16:33 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Linux)CVSS 3.18.8
Patch
Available – fixed in fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1, d5cea6766ae1868a51c7d17d77d065b4f55c587f, 63c2fbde15ffc9a0c21adf670c38d028e20fa65c +4
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1
Fixed in
  • fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < d5cea6766ae1868a51c7d17d77d065b4f55c587f
Fixed in
  • d5cea6766ae1868a51c7d17d77d065b4f55c587f
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 63c2fbde15ffc9a0c21adf670c38d028e20fa65c
Fixed in
  • 63c2fbde15ffc9a0c21adf670c38d028e20fa65c
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 7fa84c9ca690643f429ae2709584a47e74b572c9
Fixed in
  • 7fa84c9ca690643f429ae2709584a47e74b572c9
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 4e78b5ff13214353750b87283ff79f62510f5844
Fixed in
  • 4e78b5ff13214353750b87283ff79f62510f5844
LinuxLinuxAffected
  • ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd
Fixed in
  • 2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd

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)

References

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