CVE-2026-74609

Description

In the Linux kernel, the following vulnerability has been resolved: tipc: read le->link under the node lock in tipc_node_link_down() tipc_node_link_down() caches the link pointer before taking n->lock: struct tipc_link *l = le->link; /* unlocked */ if (!l) return; tipc_node_write_lock(n); if (!tipc_link_is_establishing(l)) { /* deref l */ ... tipc_link_reset(l); /* write into l */ if (delete) { kfree(l); le->link = NULL; The delete=true caller frees that very object under n->lock, so the lock does not protect the cached pointer against it: - CPU A, delete=false: tipc_rcv() on TIPC_LINK_DOWN_EVT, or the link supervision timer via tipc_node_timeout(), reads l unlocked and then dereferences it under n->lock; - CPU B, delete=true: netlink TIPC_NL_BEARER_DISABLE -> bearer_disable() -> tipc_node_delete_links() -> tipc_node_link_down(n, bearer_id, true) -> kfree(l). The link is freed with plain kfree(), not kfree_rcu(), and for UDP bearers disable_media() only schedules the asynchronous cleanup_bearer() work, so its synchronize_net() runs after the links are already gone. An in-flight CPU A that has read l therefore dereferences freed memory once B frees it: a use-after-free read in tipc_link_is_establishing(), and a use-after-free write via tipc_link_reset() on the establishing branch. The following trace was captured on 7.2.0-rc5-00284-gaf39eb111ce6: BUG: KASAN: slab-use-after-free in tipc_link_is_establishing (net/tipc/link.c:285) Read of size 4 at addr ffff88802e2aa068 by task swapper/2/0 tipc_link_is_establishing (net/tipc/link.c:285) tipc_node_link_down (net/tipc/node.c:1076) tipc_node_timeout (net/tipc/node.c:843) Allocated by task 9549: tipc_link_create (net/tipc/link.c:490) tipc_node_check_dest (net/tipc/node.c:1279) tipc_disc_rcv (net/tipc/discover.c:252) tipc_udp_recv (net/tipc/udp_media.c:389) Freed by task 9549: tipc_node_link_down (net/tipc/node.c:1084) tipc_node_delete_links (net/tipc/node.c:1320) bearer_disable (net/tipc/bearer.c:414) __tipc_nl_bearer_disable (net/tipc/bearer.c:992) Move the le->link read inside tipc_node_write_lock(), so it is serialised against the kfree() in the delete path. A racing teardown now either has not run yet, and we see a valid link, or has already run, and we see NULL.

Gravité et risque d'exploitation

CVE-2026-74609 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 0.13 %, ce qui la place devant 2.0 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 6.6.152, 0, <=7.1.*, <c3f2347a47754eac690967cfd82cb6d559817b07, 5.15.216, <5558a8312452ddb21eff22b1cbd84302ad951944, 4.4, <=5.10.*, <=6.6.*, <47ba70891b10b2feb52462086b7fcd2ad75d3ce3, 7.1.9, <a714d62513befef37f71f4ae89bb1fe173b65f2e, 6.1.183, <=6.18.*, 6.12.104, 73f646cec35477b5099d7e952297cb9e1855be45, 6.18.45, <=*, <=5.15.*, <cba9ccb47e9fa4cc77692fb896cc5ab57a667882, <de017c22135f545ca4e65d1eada22887b64958eb, <2be741ad565c610871a6a95062c12c39da7168fd, <69d209461c110388710e483a130caf051e4fd09a, 5.10.265, 7.2, <4.4) 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/2be741ad565c610871a6a95062c12c39da7168fd
• https://git.kernel.org/stable/c/69d209461c110388710e483a130caf051e4fd09a
• https://git.kernel.org/stable/c/de017c22135f545ca4e65d1eada22887b64958eb
• https://git.kernel.org/stable/c/47ba70891b10b2feb52462086b7fcd2ad75d3ce3
• https://git.kernel.org/stable/c/a714d62513befef37f71f4ae89bb1fe173b65f2e
• https://git.kernel.org/stable/c/c3f2347a47754eac690967cfd82cb6d559817b07
• https://git.kernel.org/stable/c/5558a8312452ddb21eff22b1cbd84302ad951944
• https://git.kernel.org/stable/c/cba9ccb47e9fa4cc77692fb896cc5ab57a667882