CVE-2026-74493 net/smc: fix socket use-after-free during link group termination
A race condition in the Linux kernel SMC module allows a use-after-free during link group termination, potentially leading to code execution or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74493?
CVE-2026-74493 is a critical use after free vulnerability in Linux, published on 15 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 socket use-after-free during link group termination
__smc_lgr_terminate() drops conns_lock after finding a connection in lgr->conns_all, but before taking a reference on its socket. The connection is embedded in the socket, and its registration reference protects it only while the connection remains in the tree.
A concurrent close can unregister the connection and drop that reference, freeing the socket before the termination worker reaches sock_hold().
The race is reachable when close overlaps link group termination. Local stress testing reproduced the use-after-free and KASAN reported:
BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc] Write of size 4 by task kworker/3:3 Workqueue: events smc_lgr_terminate_work [smc] __smc_lgr_terminate.part.0 [smc]
The socket was allocated by smc_create(), freed through slab_free_after_rcu_debug(), and was followed by:
refcount_t: addition on 0; use-after-free. __smc_lgr_terminate.part.0 [smc]
Take the socket reference while conns_lock still protects the tree entry. The unregister path then cannot drop the last reference until termination has finished using the socket.
Which versions are affected by CVE-2026-74493?
How do I fix CVE-2026-74493?
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-2026-74493 being exploited?
There is no known exploitation of CVE-2026-74493 in the wild and no public exploit code.
Sources
Also known as AZL-96326, BELL-CVE-2026-74493, DEBIAN-CVE-2026-74493, GHSA-xhjj-46q7-2hx6, UBUNTU-CVE-2026-74493.