CVE-2026-31663 xfrm: hold dev ref until after transport_finish NF_HOOK
A race condition in the Linux kernel's xfrm subsystem allows a use-after-free, potentially leading to code execution or denial of service.
- 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-2026-31663?
CVE-2026-31663 is a high-severity use after free vulnerability in Linux kernel, published on 24 Apr 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: hold dev ref until after transport_finish NF_HOOK
After async crypto completes, xfrm_input_resume() calls dev_put() immediately on re-entry before the skb reaches transport_finish. The skb->dev pointer is then used inside NF_HOOK and its okfn, which can race with device teardown.
Remove the dev_put from the async resumption entry and instead drop the reference after the NF_HOOK call in transport_finish, using a saved device pointer since NF_HOOK may consume the skb. This covers NF_DROP, NF_QUEUE and NF_STOLEN paths that skip the okfn.
For non-transport exits (decaps, gro, drop) and secondary async return points, release the reference inline when async is set.
Which versions are affected by CVE-2026-31663?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31663?
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-2026-31663 being exploited?
There is no known exploitation of CVE-2026-31663 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83720, BELL-CVE-2026-31663, DEBIAN-CVE-2026-31663, GHSA-v4m9-vrgr-8xm2, ROOT-OS-DEBIAN-11-CVE-2026-31663, ROOT-OS-DEBIAN-12-CVE-2026-31663 and 4 more.