CVE-2026-64525

CVE CVE-2026-64525EUVD EUVD-2026-49037Published 2026-07-25T09:20:49.000Z

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 33a3149dd81a1e2f52b80ee1e0fc380b39f3d028; patch: 7.0.12; patch: 0; 069daad4f2ae9c5c108131995529d5f02392c446 <d14ae8ef88c2c6590e107db61b6adce148cec7b3; 6.18.24 <6.18.35; 7.0; 069daad4f2ae9c5c108131995529d5f02392c446 <3e52417318473782012b236d0325bf7d2266a597; b66920a3348c0f63ba18365248fa21fbf0b3a937; patch: 6.12.93; 6.12.83 <6.12.93; 6.6.136 <6.7; patch: 6.18.35; 3733fce2871c9bca9dd18a1a23b1432ea215a094 <91cc13978ab0bc6f669139f53e7e613a860d10e0; 6.19.14 <6.20; 438b1f668ad58f46ce699bb48e4698a7839e3f9e <bca6386dc08750fc7cdcbc7683473748ba3114b9; patch: 7.1

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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