CVE-2026-68338 net/packet: avoid fanout hook re-registration after unregister
A race condition in the Linux kernel packet socket implementation can lead to invalid hook re-registration, potentially causing system instability or denial of service.
- 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-2026-68338?
CVE-2026-68338 is a high-severity vulnerability in Linux, published on 10 Aug 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/packet: avoid fanout hook re-registration after unregister
packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value.
That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered.
Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket.
Weakness: CWE-362
Which versions are affected by CVE-2026-68338?
How do I fix CVE-2026-68338?
Apply the vendor's patch.
Is CVE-2026-68338 being exploited?
There is no known exploitation of CVE-2026-68338 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68338, DEBIAN-CVE-2026-68338, GHSA-xrw5-g7cv-c5p3, UBUNTU-CVE-2026-68338.