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CVE-2026-31703

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.8 · Élevée
EPSS 0.2%
Linux•Linux•Versions : 7.0.2, <=7.0.*, <9223e5f30403a9b506d6d0bff4f2e29a2d7d46af, <156cc63691c1f20905510b1007896e090355e6c2, fabfc1fcddc5d8185722d4fde5f0968c4760b71e, 0, <19ec404b079be057b387643ba0c69bbcc5867c35, 6.18.25, 6.18, d072b38a64ddbc2d58c2e525a24af24ecbfebcb7, 7.1, <028103656b84273c73e9e271cf95c9f3421f4b8a, <=6.18.*, <6689f01d6740cf358932b3e97ee968c6099800d9, e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b, <6.18, <=*, ac7b2c21f2269d815ad0cdf0f8258d55185b805c, <382cf81cae89e58d22b4bdc38891cd4d0b9ba921

Description

In the Linux kernel, the following vulnerability has been resolved: writeback: Fix use after free in inode_switch_wbs_work_fn() inode_switch_wbs_work_fn() has a loop like: wb_get(new_wb); while (1) { list = llist_del_all(&new_wb->switch_wbs_ctxs); /* Nothing to do? */ if (!list) break; ... process the items ... } Now adding of items to the list looks like: wb_queue_isw() if (llist_add(&isw->list, &wb->switch_wbs_ctxs)) queue_work(isw_wq, &wb->switch_work); Because inode_switch_wbs_work_fn() loops when processing isw items, it can happen that wb->switch_work is pending while wb->switch_wbs_ctxs is empty. This is a problem because in that case wb can get freed (no isw items -> no wb reference) while the work is still pending causing use-after-free issues. We cannot just fix this by cancelling work when freeing wb because that could still trigger problematic 0 -> 1 transitions on wb refcount due to wb_get() in inode_switch_wbs_work_fn(). It could be all handled with more careful code but that seems unnecessarily complex so let's avoid that until it is proven that the looping actually brings practical benefit. Just remove the loop from inode_switch_wbs_work_fn() instead. That way when wb_queue_isw() queues work, we are guaranteed we have added the first item to wb->switch_wbs_ctxs and nobody is going to remove it (and drop the wb reference it holds) until the queued work runs.

Gravité et risque d'exploitation

CVE-2026-31703 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 0.17 %, ce qui la place devant 6.0 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions 7.0.2, <=7.0.*, <9223e5f30403a9b506d6d0bff4f2e29a2d7d46af, <156cc63691c1f20905510b1007896e090355e6c2, fabfc1fcddc5d8185722d4fde5f0968c4760b71e, 0, <19ec404b079be057b387643ba0c69bbcc5867c35, 6.18.25, 6.18, d072b38a64ddbc2d58c2e525a24af24ecbfebcb7, 7.1, <028103656b84273c73e9e271cf95c9f3421f4b8a, <=6.18.*, <6689f01d6740cf358932b3e97ee968c6099800d9, e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b, <6.18, <=*, ac7b2c21f2269d815ad0cdf0f8258d55185b805c, <382cf81cae89e58d22b4bdc38891cd4d0b9ba921) 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

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