smb: client: reject a tree connect response whose byte count is too small
In the Linux kernel, the following vulnerability has been resolved: smb: client: reject a tree connect response whose byte count is too small CIFSTCon() bounds its strnlen() over the byte area with the server's ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int and converts to a huge size_t. The later subtraction wraps the __u16 bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the slab object, and the bytes reach userspace through tcon->nativeFileSystem in /proc/fs/cifs/DebugData. Reject a byte area too small for what the parser consumes. Two bytes is the least it can consume, and no conformant response carries fewer. The new trace point is the 129th smb_eio_trace entry, which __mode(byte) cannot represent, so the attribute goes with it.
CVE-2026-89631
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-2026-89631
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": "cc20c031bb067eb3280a1c4b5c42295093e24863",
"lessThan": "d837645a719151ed392d4d9cab4571c2753dab12",
"versionType": "git"
},
{
"status": "affected",
"version": "cc20c031bb067eb3280a1c4b5c42295093e24863",
"lessThan": "2ae219762ebac929bf6ab3473681f10ed566af08",
"versionType": "git"
},
{
"status": "affected",
"version": "cc20c031bb067eb3280a1c4b5c42295093e24863",
"lessThan": "3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d",
"versionType": "git"
},
{
"status": "affected",
"version": "cc20c031bb067eb3280a1c4b5c42295093e24863",
"lessThan": "411e484fe71a7f1028de617447edad9cb6d9d68a",
"versionType": "git"
},
{
"status": "affected",
"version": "cc20c031bb067eb3280a1c4b5c42295093e24863",
"lessThan": "65deb18359341141d37dc86fc7853511be3c87a7",
"versionType": "git"
}
],
"programFiles": [
"fs/smb/client/cifssmb.c",
"fs/smb/client/trace.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.30"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.30",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.114",
"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/cifssmb.c",
"fs/smb/client/trace.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89631
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #46690 · Revision 1
- Added to Heist Feed
- Publisher date