CVE-2026-74692 net/smc: fix TOCTOU race between smc_listen_out() and listener close
A race condition in the Linux kernel SMC module allows remote attackers to exhaust kernel memory and cause denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74692?
CVE-2026-74692 is a high-severity vulnerability in Linux, published on 22 Aug 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/smc: fix TOCTOU race between smc_listen_out() and listener close
smc_listen_out() reads lsmc->sk.sk_state without the listener lock, then acquires lock_sock_nested() only after the check passes. This opens a window where smc_close_active() can transition the listener to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept queue, and release the lock, all between the lockless read and the delayed lock acquisition:
smc_listen_work (smc_hs_wq) smc_close_active() ------------------------------- ------------------------- release_sock(child) if (sk_state == SMC_LISTEN) TRUE lock_sock(listener) sk_state = SMC_CLOSED smc_close_cleanup_listen() release_sock(listener) flush_work(tcp_listen_work) lock_sock_nested(listener) smc_accept_enqueue(listener, child) /* child enqueued on dead listener */
smc_close_active() flushes only tcp_listen_work. Work items already dispatched onto smc_hs_wq for the CLC handshake continue running unguarded. smc_accept_enqueue() takes a sock_hold() on the child that is never released, so the child smc_sock, its clcsock, and the reference all leak. A remote peer that opens TCP connections while the server calls close() can exhaust kernel memory.
Move lock_sock_nested() to before the sk_state check so that the test and the enqueue are atomic under the listener lock.
Which versions are affected by CVE-2026-74692?
How do I fix CVE-2026-74692?
Apply the vendor's patch.
Is CVE-2026-74692 being exploited?
There is no known exploitation of CVE-2026-74692 in the wild and no public exploit code.
Sources
Also known as AZL-97083, BELL-CVE-2026-74692, DEBIAN-CVE-2026-74692, GHSA-r9r5-95ff-67hq, UBUNTU-CVE-2026-74692.