CVE-2026-68137 net/x25: fix use-after-free in x25_kill_by_neigh()
A use-after-free in the Linux kernel X.25 network stack allows attackers to execute arbitrary code or escalate privileges via concurrent socket operations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68137?
CVE-2026-68137 is a critical use after free vulnerability in Linux, published on 10 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/x25: fix use-after-free in x25_kill_by_neigh()
x25_kill_by_neigh() walks the global X.25 socket list looking for sockets attached to a terminating neighbour. x25_list_lock protects list membership while the lookup is in progress, but it does not pin a socket's lifetime after the lock is dropped.
The function currently drops x25_list_lock before calling lock_sock(s). A concurrent close can run x25_release(), remove the same socket from x25_list, and drop the last socket reference in that window. The neighbour teardown path can then lock or inspect a freed struct sock/struct x25_sock.
Take sock_hold(s) while x25_list_lock still proves that the list entry is live, then drop the temporary reference after the socket has been locked, rechecked, and released. Recheck x25_sk(s)->neighbour after lock_sock(), because another path may have disconnected the socket before this path acquired the socket lock. Restart the list walk after each disconnect because the list lock was dropped and the previous iterator state may no longer be valid.
A QEMU/KASAN run against origin/master reproduced a slab-use-after-free in x25_kill_by_neigh().
Which versions are affected by CVE-2026-68137?
How do I fix CVE-2026-68137?
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-2026-68137 being exploited?
There is no known exploitation of CVE-2026-68137 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68137, DEBIAN-CVE-2026-68137, GHSA-8pjr-r8qw-rq6v, UBUNTU-CVE-2026-68137.