CVE-2026-45918 ovpn: tcp - don't deref NULL sk_socket member after tcp_close()
A race condition in the Linux kernel's OpenVPN TCP implementation causes a null pointer dereference, leading to a system crash.
- 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-2026-45918?
CVE-2026-45918 is a medium-severity vulnerability in Linux kernel, published on 27 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:
ovpn: tcp - don't deref NULL sk_socket member after tcp_close()
When deleting a peer in case of keepalive expiration, the peer is removed from the OpenVPN hashtable and is temporary inserted in a "release list" for further processing.
This happens in: ovpn_peer_keepalive_work() unlock_ovpn(release_list)
This processing includes detaching from the socket being used to talk to this peer, by restoring its original proto and socket ops/callbacks.
In case of TCP it may happen that, while the peer is sitting in the release list, userspace decides to close the socket. This will result in a concurrent execution of:
tcp_close(sk) __tcp_close(sk) sock_orphan(sk) sk_set_socket(sk, NULL)
The last function call will set sk->sk_socket to NULL.
When the releasing routine is resumed, ovpn_tcp_socket_detach() will attempt to dereference sk->sk_socket to restore its original ops member. This operation will crash due to sk->sk_socket being NULL.
Fix this race condition by testing-and-accessing sk->sk_socket atomically under sk->sk_callback_lock.
Weakness: CWE-476
Which versions are affected by CVE-2026-45918?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45918?
Apply the vendor's patch.
Is CVE-2026-45918 being exploited?
There is no known exploitation of CVE-2026-45918 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-45918, DEBIAN-CVE-2026-45918, GHSA-478p-qchq-q398, UBUNTU-CVE-2026-45918.