CVE-2026-68100ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl
- 8.1HighCVSS base score
- 0.43%Exploitation in 30 daysEPSS · top 62% 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: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl().
Timeline
ID reserved
By Linux
- 11 days later
· 11 days later
Published
- 2 months later
· 2 months 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 | High8.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
| NVDNVD · Received | 3.1 | High8.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.43% · top 62% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.1.
Affected products
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 26cb845e22a00c85bf566337417fa33492395f10
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < e31fada5143784bc05c7ae44c79eed9b7a2e147e
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < fb3dc8e6da46a1ccad1956cda57de29d9b3033e0
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < b6d3cc6a524416dfdb2b47e4bba2e7e20011d056
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 5acbd3012fd4a7ccfebd91ea6f784120084eb897
- affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 – < 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d
- affected 5.15
- unaffected < 5.15
- unaffected 6.1.184 – ≤ 6.1.*
- unaffected 6.6.148 – ≤ 6.6.*
- unaffected 6.12.101 – ≤ 6.12.*
- unaffected 6.18.42 – ≤ 6.18.*
- unaffected 7.1.6 – ≤ 7.1.*
- unaffected 7.2 – ≤ *
References
References6
- https://git.kernel.org/stable/c/26cb845e22a00c85bf566337417fa33492395f10 (opens in a new tab)
- https://git.kernel.org/stable/c/e31fada5143784bc05c7ae44c79eed9b7a2e147e (opens in a new tab)
- https://git.kernel.org/stable/c/fb3dc8e6da46a1ccad1956cda57de29d9b3033e0 (opens in a new tab)
- https://git.kernel.org/stable/c/b6d3cc6a524416dfdb2b47e4bba2e7e20011d056 (opens in a new tab)
- https://git.kernel.org/stable/c/5acbd3012fd4a7ccfebd91ea6f784120084eb897 (opens in a new tab)
- https://git.kernel.org/stable/c/47f0b34f6bc98ed85bfdc293e8f3e432ec24958d (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-2026-55481 (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-2026-68100)Record last updated .