CVE-2026-97555smb: client: fix heap overflow in DACL owner/group rewrite
- 8.8HighCVSS base score
- 0.58%Exploitation in 30 daysEPSS · top 52% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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)
Timeline
ID reserved
By Linux
- 1 day later
· 1 day later
Published
- 35 days later
· 35 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.58% · top 52% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.
Affected products
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < 4e78b5ff13214353750b87283ff79f62510f5844
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < 63c2fbde15ffc9a0c21adf670c38d028e20fa65c
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < d5cea6766ae1868a51c7d17d77d065b4f55c587f
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < 7fa84c9ca690643f429ae2709584a47e74b572c9
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < 2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd
- affected bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 – < 0ee150794c75bcd0be0e24ff3394f433cbae18cc
- affected 5.12
- unaffected < 5.12
- unaffected 5.15.224 – ≤ 5.15.*
- unaffected 6.1.191 – ≤ 6.1.*
- unaffected 6.6.158 – ≤ 6.6.*
- unaffected 6.12.111 – ≤ 6.12.*
- unaffected 6.18.53 – ≤ 6.18.*
- unaffected 7.2.7 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References7
- https://git.kernel.org/stable/c/4e78b5ff13214353750b87283ff79f62510f5844 (opens in a new tab)
- https://git.kernel.org/stable/c/63c2fbde15ffc9a0c21adf670c38d028e20fa65c (opens in a new tab)
- https://git.kernel.org/stable/c/d5cea6766ae1868a51c7d17d77d065b4f55c587f (opens in a new tab)
- https://git.kernel.org/stable/c/fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1 (opens in a new tab)
- https://git.kernel.org/stable/c/7fa84c9ca690643f429ae2709584a47e74b572c9 (opens in a new tab)
- https://git.kernel.org/stable/c/2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd (opens in a new tab)
- https://git.kernel.org/stable/c/0ee150794c75bcd0be0e24ff3394f433cbae18cc (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-86863 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-97555)Record last updated .