CVE-2026-63980 net/handshake: Use spin_lock_bh for hn_lock
A deadlock in the Linux kernel's network handshake module can cause a denial of service when a softirq interrupts a process holding a lock.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63980?
CVE-2026-63980 is a high-severity vulnerability in Linux, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/handshake: Use spin_lock_bh for hn_lock
nvmet_tcp_state_change(), a socket callback that runs in BH context, can reach handshake_req_cancel() via nvmet_tcp_schedule_release_queue() and tls_handshake_cancel(). handshake_req_cancel() acquires hn->hn_lock with plain spin_lock(). If a process-context thread on the same CPU holds hn->hn_lock when a softirq invokes the cancel path, the lock attempt deadlocks. This is the only caller that invokes tls_handshake_cancel() from BH context; every other consumer calls it from process context.
Deferring the cancel to process context in the NVMe target is not straightforward: nvmet_tcp_schedule_release_queue() must call tls_handshake_cancel() atomically with its state transition to DISCONNECTING. If the cancel were deferred, the handshake completion callback could fire in the window before the cancel runs, observe the unexpected state, and return without dropping its kref on the queue. Reworking that interlock is considerably more invasive than hardening the handshake lock. Convert all hn->hn_lock acquisitions from spin_lock/spin_unlock to spin_lock_bh/spin_unlock_bh so the lock is never taken with softirqs enabled.
Weakness: CWE-362
Which versions are affected by CVE-2026-63980?
How do I fix CVE-2026-63980?
Apply the vendor's patch.
Is CVE-2026-63980 being exploited?
There is no known exploitation of CVE-2026-63980 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63980, DEBIAN-CVE-2026-63980, GHSA-pf6j-pgmp-5g96, UBUNTU-CVE-2026-63980.