CVE-2025-21864

Description

In the Linux kernel, the following vulnerability has been resolved: tcp: drop secpath at the same time as we currently drop dst Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while running tests that boil down to: - create a pair of netns - run a basic TCP test over ipcomp6 - delete the pair of netns The xfrm_state found on spi_byaddr was not deleted at the time we delete the netns, because we still have a reference on it. This lingering reference comes from a secpath (which holds a ref on the xfrm_state), which is still attached to an skb. This skb is not leaked, it ends up on sk_receive_queue and then gets defer-free'd by skb_attempt_defer_free. The problem happens when we defer freeing an skb (push it on one CPU's defer_list), and don't flush that list before the netns is deleted. In that case, we still have a reference on the xfrm_state that we don't expect at this point. We already drop the skb's dst in the TCP receive path when it's no longer needed, so let's also drop the secpath. At this point, tcp_filter has already called into the LSM hooks that may require the secpath, so it should not be needed anymore. However, in some of those places, the MPTCP extension has just been attached to the skb, so we cannot simply drop all extensions.

Gravité et risque d'exploitation

CVE-2025-21864 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 0.28 %, ce qui la place devant 18.9 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <69cafd9413084cd5012cf5d7c7ec6f3d493726d9, <=6.12.*, 6.1.130, 0, 5.19, <cd34a07f744451e2ecf9005bb7d24d0b2fb83656, 6.14, <=6.6.*, 6.6.80, <87858bbf21da239ace300d61dd209907995c0491, 6.13.5, 6.12.17, <5.19, <=*, <=6.13.*, <9b6412e6979f6f9e0632075f8f008937b5cd4efd, <f1d5e6a5e468308af7759cf5276779d3155c5e98, 68822bdf76f10c3dc80609d4e2cdc1e847429086) 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/87858bbf21da239ace300d61dd209907995c0491
• https://git.kernel.org/stable/c/f1d5e6a5e468308af7759cf5276779d3155c5e98
• https://git.kernel.org/stable/c/cd34a07f744451e2ecf9005bb7d24d0b2fb83656
• https://git.kernel.org/stable/c/69cafd9413084cd5012cf5d7c7ec6f3d493726d9
• https://git.kernel.org/stable/c/9b6412e6979f6f9e0632075f8f008937b5cd4efd