smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()
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.
CVE-2026-89633
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-89633
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
"lessThan": "6eb70b78e48b0031bd1a05fe1b58959a48e87739",
"versionType": "git"
},
{
"status": "affected",
"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
"lessThan": "36d01415d881d5326a0dd3384f781cd7e69aff2d",
"versionType": "git"
},
{
"status": "affected",
"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
"lessThan": "672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e",
"versionType": "git"
},
{
"status": "affected",
"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
"lessThan": "033bc80019f07d158630df4e69b19a49010f54f1",
"versionType": "git"
},
{
"status": "affected",
"version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
"lessThan": "6343c1da561962688f203362d80d6a3bfa39fa1b",
"versionType": "git"
}
],
"programFiles": [
"fs/smb/client/smb1transport.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.113",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/smb/client/smb1transport.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89633
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #46691 · Revision 1
- Added to Heist Feed
- Publisher date