CVE-2026-63795
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.
Affected versions
Linux kernel versions
6.0
and later are affected. Fixed in
6.1.177,
6.6.144,
6.12.95,
6.18.38,
7.1.3,
7.2-rc1
and their respective stable series.
References
6 totalFrequently asked questions
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What is CVE-2026-63795?
CVE-2026-63795 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 6.0 onward and has been patched in 6.1.177, 6.6.144, 6.12.95 and others. CVE-2026-63795 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-63795?
Yes — CVE-2026-63795 has been patched. Fixed versions include 6.1.177, 6.6.144, 6.12.95 and others. If you are running Linux kernel 6.0 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-63795 actively exploited?
No — CVE-2026-63795 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.