CVE-2026-31477

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix memory leaks and NULL deref in smb2_lock() smb2_lock() has three error handling issues after list_del() detaches smb_lock from lock_list at no_check_cl: 1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK path, goto out leaks smb_lock and its flock because the out: handler only iterates lock_list and rollback_list, neither of which contains the detached smb_lock. 2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out leaks smb_lock and flock for the same reason. The error code returned to the dispatcher is also stale. 3) In the rollback path, smb_flock_init() can return NULL on allocation failure. The result is dereferenced unconditionally, causing a kernel NULL pointer dereference. Add a NULL check to prevent the crash and clean up the bookkeeping; the VFS lock itself cannot be rolled back without the allocation and will be released at file or connection teardown. Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before the if(!rc) check in the UNLOCK branch so all exit paths share one free site, and by freeing smb_lock and flock before goto out in the non-UNLOCK branch. Propagate the correct error code in both cases. Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding a NULL check for locks_free_lock(rlock) in the shared cleanup. Found via call-graph analysis using sqry.

Gravité et risque d'exploitation

CVE-2026-31477 obtient un score CVSS de 7.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.68 %, ce qui la place devant 51.6 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 0, 7.0, <cdac6f7e7e428dc70e3b5898ac6999a72ed13993, <91aeaa7256006d79a37298f5a1df23325db91599, <=6.6.*, 6.19.11, <=6.19.*, <5.15, e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9, <c9b95ef6f5039f19e46c3a521a4fe1752d91dfe9, <3cdacd11b41569ce75b3162142240f2355e04900, 5.15, <=6.18.*, 6.6.131, <aab42f0795620cf0d3955a520f571f697d0f9a2a, 6.12.80, <=*, 6.1.168, 6.18.21, <309b44ed684496ed3f9c5715d10b899338623512) 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/cdac6f7e7e428dc70e3b5898ac6999a72ed13993
• https://git.kernel.org/stable/c/c9b95ef6f5039f19e46c3a521a4fe1752d91dfe9
• https://git.kernel.org/stable/c/91aeaa7256006d79a37298f5a1df23325db91599
• https://git.kernel.org/stable/c/3cdacd11b41569ce75b3162142240f2355e04900
• https://git.kernel.org/stable/c/aab42f0795620cf0d3955a520f571f697d0f9a2a
• https://git.kernel.org/stable/c/309b44ed684496ed3f9c5715d10b899338623512