CVE-2026-97555: Linux kernel · smb: client: fix heap overflow in DACL owner/group rewrite
Source GCVE Database
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
Thin evidence
One scorer or none| CNA (Linux) | CVSS 3.1 | 8.8 |
|---|
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- nvd.nist.gov/vuln/detail/CVE-2026-97555 (opens in a new tab)
- git.kernel.org/stable/c/0ee150794c75bcd0be0e24ff3394f433cbae18cc (opens in a new tab)
- git.kernel.org/stable/c/2a9aee9ef5622d58d8aafaa3263b3ffe70e2d9dd (opens in a new tab)
- git.kernel.org/stable/c/4e78b5ff13214353750b87283ff79f62510f5844 (opens in a new tab)
- git.kernel.org/stable/c/63c2fbde15ffc9a0c21adf670c38d028e20fa65c (opens in a new tab)
- git.kernel.org/stable/c/7fa84c9ca690643f429ae2709584a47e74b572c9 (opens in a new tab)
- git.kernel.org/stable/c/d5cea6766ae1868a51c7d17d77d065b4f55c587f (opens in a new tab)
- git.kernel.org/stable/c/fb736ab4fb8c4fdb8b2f9ccd3a62e03d11549ca1 (opens in a new tab)