CVE-2026-63795

Description

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.

Gravité et risque d'exploitation

CVE-2026-63795 obtient un score CVSS de 10.0/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.50 %, ce qui la place devant 41.8 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 6.6.144, 0, <=7.1.*, <=6.6.*, 6.12.95, 6.0, <6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea, <a61bdcba4f64c2f90d01461913f429ab151f1ca6, b48dbb998d70b7f48c2ec0a15c3cf47136808e4e, <6.0, <a7656d368265d085ac9bb85ab31b0cdb72ad8c38, <=6.18.*, <1a3860d46e3eb47dbd60339783cdad7904486b9f, 6.1.177, 6.18.38, <b84f46179c806450b89821221ea5bd9a1698aba8, <=*, 7.1.3, 7.2, <99c379ca1e221c3d75c7c804ebbf4e5ee37a3070) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/99c379ca1e221c3d75c7c804ebbf4e5ee37a3070
• https://git.kernel.org/stable/c/b84f46179c806450b89821221ea5bd9a1698aba8
• https://git.kernel.org/stable/c/a61bdcba4f64c2f90d01461913f429ab151f1ca6
• https://git.kernel.org/stable/c/6dbe9443d9f5f7fb6d319a7b77108853ae6c6bea
• https://git.kernel.org/stable/c/a7656d368265d085ac9bb85ab31b0cdb72ad8c38
• https://git.kernel.org/stable/c/1a3860d46e3eb47dbd60339783cdad7904486b9f