9p: avoid putting oldfid in p9_client_walk() error path
In the Linux kernel, the following vulnerability has been resolved: 9p: avoid putting oldfid in p9_client_walk() error path When p9_client_walk() is called with clone set to false, fid aliases oldfid. If the walk subsequently fails after the request has been sent, the error path jumps to clunk_fid, which currently calls p9_fid_put(fid) unconditionally. This drops a reference to oldfid even though ownership of oldfid remains with the caller. If this is the last reference, oldfid can be clunked and destroyed while the caller still expects it to be valid. A later use or put of oldfid can then trigger a use-after-free or refcount underflow. Fix this by only putting fid in the clunk_fid error path when it does not alias oldfid, matching the existing guard in the error path below. This can be triggered when a multi-component walk is split into multiple p9_client_walk() calls and a later non-cloning walk fails. A reproducer and refcount warning logs are available on request.
CVE-2026-63795
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-2026-63795
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": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "99c379ca1e221c3d75c7c804ebbf4e5ee37a3070",
"versionType": "git"
},
{
"status": "affected",
"version": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "b84f46179c806450b89821221ea5bd9a1698aba8",
"versionType": "git"
},
{
"status": "affected",
"version": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "a61bdcba4f64c2f90d01461913f429ab151f1ca6",
"versionType": "git"
},
{
"status": "affected",
"version": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea",
"versionType": "git"
},
{
"status": "affected",
"version": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "a7656d368265d085ac9bb85ab31b0cdb72ad8c38",
"versionType": "git"
},
{
"status": "affected",
"version": "b48dbb998d70b7f48c2ec0a15c3cf47136808e4e",
"lessThan": "1a3860d46e3eb47dbd60339783cdad7904486b9f",
"versionType": "git"
}
],
"programFiles": [
"net/9p/client.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.1.177",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.144",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.95",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/9p/client.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-63795
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #40828 · Revision 1
- Added to Heist Feed
- Publisher date