CVE-2026-53175

Description

In the Linux kernel, the following vulnerability has been resolved: inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and flushes every fragment queue that is not yet complete using inet_frag_queue_flush(). That helper frees all the skbs queued on the fragment queue but does not set INET_FRAG_COMPLETE, and leaves q->fragments_tail and q->last_run_head pointing at the freed skbs. The queue itself stays in the rhashtable. fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups, but it cannot stop a fragment that already obtained the queue through inet_frag_find() earlier and stalled just before taking the queue lock. Once that fragment resumes after the flush and takes the queue lock, it passes the INET_FRAG_COMPLETE check and then dereferences the freed fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of that pointer and, on the append path, writes ->next_frag, causing a slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly share the same flush path and are affected as well. Reset rb_fragments, fragments_tail and last_run_head in inet_frag_queue_flush() so a flushed queue no longer points at the freed skbs. A fragment that resumes after the flush and takes the queue lock then finds an empty queue and starts a new run instead of dereferencing the freed fragments_tail. ip_frag_reinit() already performed this reset after its own flush, so drop the now duplicate code there.

Gravité et risque d'exploitation

CVE-2026-53175 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 0.31 %, ce qui la place devant 22.8 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=7.0.*, c70df25214ac9b32b53e18e6ae3b8f073ffa6903, <=6.12.*, <6.19, 6.12.94, 6.12.93, 0, <6.12.94, <0e823ca0e7391630784ae7dd0981b7ad170a93d9, <c22599cc90e1cd5f8129c8670bd68a02ff7177b4, 6.18.3, 7.0.13, 6.18.36, 543555954b1ee8d1903a7020324efb41b0c97428, <010c3313a4d178dc2d3ce958d2e5cb055e2864c1, <89b909e9704587bfecc1aab1d37e98faee03b9f9, 7.1, <=6.18.*, <6.18.36, 22ee4010866da81aeee08e1ea3fddbe418feb212, <32594b09854970d7ba83eb2dc8c69a2edd158c8e, <=*, 6.19, 006a5035b495dec008805df249f92c22c89c3d2e) 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/0e823ca0e7391630784ae7dd0981b7ad170a93d9
• https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4
• https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9
• https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1
• https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e