CVE-2026-31504

Description

In the Linux kernel, the following vulnerability has been resolved: net: fix fanout UAF in packet_release() via NETDEV_UP race `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617.

Gravité et risque d'exploitation

CVE-2026-31504 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 0.14 %, ce qui la place devant 2.7 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <42156f93d123436f2a27c468f18c966b7e5db796, <=6.12.*, 0, 7.0, 3.1, <d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6, <ee642b1962caa9aa231c01abbd58bc453ae6b66e, <=5.10.*, <=6.6.*, <3.1, 6.19.11, <=6.19.*, 5.15.203, ce06b03e60fc19c680d1bf873e779bf11c2fc518, <=6.18.*, 6.6.131, <1b4c03f8892d955385c202009af7485364731bb9, <654386baef228c2992dbf604c819e4c7c35fc71b, 6.12.80, <42cfd7898eeed290c9fb73f732af1f7d6b0a703e, <=*, 5.10.253, <=5.15.*, <ceccbfc6de720ad633519a226715989cfb065af1, 6.1.168, <75fe6db23705a1d55160081f7b37db9665b1880b, 6.18.21) 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/ee642b1962caa9aa231c01abbd58bc453ae6b66e
• https://git.kernel.org/stable/c/42cfd7898eeed290c9fb73f732af1f7d6b0a703e
• https://git.kernel.org/stable/c/1b4c03f8892d955385c202009af7485364731bb9
• https://git.kernel.org/stable/c/654386baef228c2992dbf604c819e4c7c35fc71b
• https://git.kernel.org/stable/c/75fe6db23705a1d55160081f7b37db9665b1880b
• https://git.kernel.org/stable/c/d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6
• https://git.kernel.org/stable/c/ceccbfc6de720ad633519a226715989cfb065af1
• https://git.kernel.org/stable/c/42156f93d123436f2a27c468f18c966b7e5db796