CVE-2026-43091 xfrm: Wait for RCU readers during policy netns exit
A use-after-free vulnerability in the Linux kernel's xfrm policy teardown allows attackers to cause denial of service or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43091?
CVE-2026-43091 is a high-severity use after free vulnerability in Linux kernel, published on 6 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-416
Which versions are affected by CVE-2026-43091?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43091?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-43091 being exploited?
There is no known exploitation of CVE-2026-43091 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43091, DEBIAN-CVE-2026-43091, GHSA-jrph-46wx-r2g3, ROOT-OS-DEBIAN-11-CVE-2026-43091, ROOT-OS-DEBIAN-12-CVE-2026-43091, ROOT-OS-UBUNTU-2204-CVE-2026-43091 and 2 more.