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.
Published: 2026-09-11
Score: 7.1 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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History

Sat, 12 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H'}

threat_severity

Important

Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
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.
Title smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-11T19:45:28.083Z

Reserved: 2026-09-11T19:38:34.739Z

Link: CVE-2026-89633

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-11T20:19:48.887

Modified: 2026-09-11T20:19:48.887

Link: CVE-2026-89633

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-11T19:45:28Z

Links: CVE-2026-89633 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-12T06:30:09Z

Weaknesses