CVE-2026-43091: xfrm: Wait for RCU readers during policy netns exit

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-06 · updated 2026-10-30
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: Wait for RCU readers during policy netns exit xfrm_policy_fini() frees the policy_bydst hash tables after flushing the policy work items and deleting all policies, but it does not wait for concurrent RCU readers to leave their read-side critical sections first. The policy_bydst tables are published via rcu_assign_pointer() and are looked up through rcu_dereference_check(), so netns teardown must also wait for an RCU grace period before freeing the table memory. Fix this by adding synchronize_rcu() before freeing the policy hash tables.

Affected products

Linux kernel: from 4.9 before 6.6.136; from 6.7 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4, 7.0-rc5, 7.0-rc6 (+1) — fixed in 6.6.136, 6.12.83, 6.18.24, 6.19.14
Linux: 4.9 — fixed in 7.0

How to fix

Upgrade to a fixed version: Linux kernel 6.6.136, 6.12.83, 6.18.24, 6.19.14; Linux 7.0. Check the vendor advisory for mitigations.

References

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