CVE-2026-53274 net/smc: fix sleep-inside-lock in __smc_setsockopt() causing local DoS
A local unprivileged user can cause a kernel denial of service by triggering a sleep-inside-lock condition in the SMC socket option handler.
- 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-2026-53274?
CVE-2026-53274 is a medium-severity denial of service vulnerability in Linux kernel, published on 25 Jun 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:
net/smc: fix sleep-inside-lock in __smc_setsockopt() causing local DoS
A logic flaw in __smc_setsockopt() allows a local unprivileged user to cause a Denial of Service (DoS) by holding the socket lock indefinitely.
The function __smc_setsockopt() calls copy_from_sockptr() while holding lock_sock(sk). By passing a userfaultfd-monitored memory page (or FUSE-backed memory on systems where unprivileged userfaultfd is disabled) as the optval, an attacker can halt execution during the copy operation, keeping the lock held.
Combined with asynchronous tear-down operations like shutdown(), this exhausts the kernel wq (kworkers) and triggers the hung task watchdog.
[ 240.123456] INFO: task kworker/u8:2 blocked for more than 120 seconds. [ 240.123489] Call Trace: [ 240.123501] smc_shutdown+... [ 240.123512] lock_sock_nested+...
This patch moves the user-space copy outside the lock_sock() critical section to prevent the issue.
Which versions are affected by CVE-2026-53274?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53274?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-53274 being exploited?
There is no known exploitation of CVE-2026-53274 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90900, BELL-CVE-2026-53274, DEBIAN-CVE-2026-53274, GHSA-22m3-g27g-5h2v, ROOT-OS-UBUNTU-2404-CVE-2026-53274, UBUNTU-CVE-2026-53274.