CVE-2026-89633smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()
- 9.8CriticalCVSS base score
- 0.55%Exploitation in 30 daysEPSS · top 53% 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 OOB read/write from unvalidated DataOffset in coalesce_t2() coalesce_t2() computes data pointers directly from server-supplied DataOffset fields with no validation against buffer bounds: data_area_of_tgt = (char *)&pSMBt->hdr.Protocol + get_unaligned_le16(&pSMBt->t2_rsp.DataOffset); data_area_of_src = (char *)&pSMBs->hdr.Protocol + get_unaligned_le16(&pSMBs->t2_rsp.DataOffset); data_area_of_tgt += total_in_tgt; ... memcpy(data_area_of_tgt, data_area_of_src, total_in_src); A small DataOffset can push a pointer below the actual byte area, overwriting header fields; a large one can push it past the buffer end, causing out-of-bounds heap reads (source) or writes (target). The BCC overflow guard does not prevent this: BCC reflects how much data is present, while DataOffset controls where in the buffer it starts. The "validate target area" comment present since the function was first written in 2005 was a placeholder that was never implemented. Add lower- and upper-bound checks for both data pointers before the memcpy, and before any target header fields are modified.
Timeline
ID reserved
By Linux
Published
- 49 days later
· 49 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 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.55% · top 53% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < f7baf60435129e3a5f3500a38e3cb4c3860deed7
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 9f3a7440731a34c89ad04fef6616f185acb28401
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 531ac35abd74fb5b4aec5e19543e832613a1789d
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 6eb70b78e48b0031bd1a05fe1b58959a48e87739
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 36d01415d881d5326a0dd3384f781cd7e69aff2d
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 033bc80019f07d158630df4e69b19a49010f54f1
- affected e4eb295d38b57f4d4b956942a48887eb252d97c6 – < 6343c1da561962688f203362d80d6a3bfa39fa1b
- affected 2.6.12
- unaffected < 2.6.12
- unaffected 5.10.273 – ≤ 5.10.*
- unaffected 5.15.224 – ≤ 5.15.*
- unaffected 6.1.191 – ≤ 6.1.*
- unaffected 6.6.160 – ≤ 6.6.*
- unaffected 6.12.113 – ≤ 6.12.*
- unaffected 6.18.51 – ≤ 6.18.*
- unaffected 7.2.4 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References8
- https://git.kernel.org/stable/c/f7baf60435129e3a5f3500a38e3cb4c3860deed7 (opens in a new tab)
- https://git.kernel.org/stable/c/9f3a7440731a34c89ad04fef6616f185acb28401 (opens in a new tab)
- https://git.kernel.org/stable/c/531ac35abd74fb5b4aec5e19543e832613a1789d (opens in a new tab)
- https://git.kernel.org/stable/c/6eb70b78e48b0031bd1a05fe1b58959a48e87739 (opens in a new tab)
- https://git.kernel.org/stable/c/36d01415d881d5326a0dd3384f781cd7e69aff2d (opens in a new tab)
- https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e (opens in a new tab)
- https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1 (opens in a new tab)
- https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b (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-2026-76545 (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-2026-89633)Record last updated .