CVE-2025-40297

Description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix use-after-free due to MST port state bypass syzbot reported[1] a use-after-free when deleting an expired fdb. It is due to a race condition between learning still happening and a port being deleted, after all its fdbs have been flushed. The port's state has been toggled to disabled so no learning should happen at that time, but if we have MST enabled, it will bypass the port's state, that together with VLAN filtering disabled can lead to fdb learning at a time when it shouldn't happen while the port is being deleted. VLAN filtering must be disabled because we flush the port VLANs when it's being deleted which will stop learning. This fix adds a check for the port's vlan group which is initialized to NULL when the port is getting deleted, that avoids the port state bypass. When MST is enabled there would be a minimal new overhead in the fast-path because the port's vlan group pointer is cache-hot. [1] https://syzkaller.appspot.com/bug?extid=dd280197f0f7ab3917be

Gravité et risque d'exploitation

CVE-2025-40297 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.16 %, ce qui la place devant 4.4 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 5.18, 6.17.8, <bf3843183bc3158e5821b46f330c438ae9bd6ddb, <991fbe1680cd41a5f97c92cd3a3496315df36e4b, 0, <5.18, 6.18, <=6.6.*, <e19085b2a86addccff33ab8536fc67ebd9d52198, ec7328b59176227216c461601c6bd0e922232a9b, 6.6.117, 6.1.159, 6.12.58, <3b60ce334c1ce8b3fad7e02dcd5ed9f6646477c8, <=*, <=6.17.*, <8dca36978aa80bab9d4da130c211db75c9e00048) 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/e19085b2a86addccff33ab8536fc67ebd9d52198
• https://git.kernel.org/stable/c/3b60ce334c1ce8b3fad7e02dcd5ed9f6646477c8
• https://git.kernel.org/stable/c/bf3843183bc3158e5821b46f330c438ae9bd6ddb
• https://git.kernel.org/stable/c/991fbe1680cd41a5f97c92cd3a3496315df36e4b
• https://git.kernel.org/stable/c/8dca36978aa80bab9d4da130c211db75c9e00048