CVE-2026-89712
Vulnérabilité critique dans Linux (Linux)
Description
In the Linux kernel, the following vulnerability has been resolved: NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer. The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item. Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.
Gravité et risque d'exploitation
CVE-2026-89712 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.71 %, ce qui la place devant 52.8 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions <=6.1.*, <d9e151fea5ed706c1284adacabd869b0be745db2, <=6.12.*, 5.15.221, <659ee3da073164e1e6e40dfcbc26eeed85845f93, 5.10.270, 0, 7.2.4, 6.1.188, <5.14, <=5.10.*, <=6.6.*, 5.14, <2b59029b8f24a99b5d844af2da3950d39d36eeea, <036c1b182f4da65363e79ec0ac276edc6b7296e5, f4e44b393389c77958f7c58bf4415032b4cda15b, 6.6.157, <4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8, a4bc287943f5695209ff36bdc89f17b48d68fae7, <60680ae7243b22de3d09be990d8e23bcfc4af837, <77de363d9a1c8cd35f20482782c612cda085791a, <=6.18.*, <5.10.270, <=7.2.*, <=*, <=5.15.*, <7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9, 6.18.50, 6.12.109, 5.10.220, 7.3) 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/2b59029b8f24a99b5d844af2da3950d39d36eeea
- https://git.kernel.org/stable/c/d9e151fea5ed706c1284adacabd869b0be745db2
- https://git.kernel.org/stable/c/659ee3da073164e1e6e40dfcbc26eeed85845f93
- https://git.kernel.org/stable/c/60680ae7243b22de3d09be990d8e23bcfc4af837
- https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a
- https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8
- https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9
- https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5