CVE-2026-64525
Vulnérabilité non évaluée dans Linux (Linux)
Description
In the Linux kernel, the following vulnerability has been resolved: xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit The struct pernet_operations docstring in include/net/net_namespace.h explicitly warns against blocking RCU primitives in .exit handlers: Exit methods using blocking RCU primitives, such as synchronize_rcu(), should be implemented via exit_batch. [...] Please, avoid synchronize_rcu() at all, where it's possible. Note that a combination of pre_exit() and exit() can be used, since a synchronize_rcu() is guaranteed between the calls. xfrm_policy_fini() violates this: it calls synchronize_rcu() before freeing the policy_bydst hash tables (so no RCU reader is mid- traversal at free time), but runs from xfrm_net_ops.exit -- once per namespace -- so a cleanup_net() of N namespaces pays N full RCU grace periods serially. Use the documented pre_exit/exit split. Move the policy flush (and the workqueue drains it depends on) into a new .pre_exit handler; xfrm_policy_fini() then runs in .exit and frees the hash tables after the synchronize_rcu_expedited() that cleanup_net() guarantees between the two phases. Providing O(1) RCU grace periods per batch instead of O(N). Observed on Linux 6.18 with a workload doing unshare(CLONE_NEWNET) at ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread both stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct net accumulated in the cleanup queue, Percpu in /proc/meminfo climbed to 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and __put_net counts were balanced, ruling out a refcount leak.
Gravité et risque d'exploitation
CVE-2026-64525 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.16 %, ce qui la place devant 4.3 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions <=7.0.*, <=6.12.*, 6.12.93, 0, <bca6386dc08750fc7cdcbc7683473748ba3114b9, 6.12.83, 7.0, <6.12.93, 6.18.35, 069daad4f2ae9c5c108131995529d5f02392c446, 33a3149dd81a1e2f52b80ee1e0fc380b39f3d028, 6.6.136, <3e52417318473782012b236d0325bf7d2266a597, <91cc13978ab0bc6f669139f53e7e613a860d10e0, <6.18.35, <7.0, 438b1f668ad58f46ce699bb48e4698a7839e3f9e, <6.20, 7.1, <=6.18.*, b66920a3348c0f63ba18365248fa21fbf0b3a937, <6.7, <d14ae8ef88c2c6590e107db61b6adce148cec7b3, 3733fce2871c9bca9dd18a1a23b1432ea215a094, 7.0.12, <=*, 6.19.14, 6.18.24) 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.