CVE-2026-74666 packet: synchronize pressure clearing with ring reconfiguration
A race condition in the Linux kernel packet socket implementation can cause a null pointer dereference, leading to a 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-2026-74666?
CVE-2026-74666 is a high-severity vulnerability in Linux, published on 22 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:
packet: synchronize pressure clearing with ring reconfiguration
packet_set_ring() updates the RX ring state under sk_receive_queue.lock, but used to publish the tpacket receive mode through po->prot_hook.func after releasing that lock. packet_poll() and packet_recvmsg() can then run the pressure clearing path after the ring has been cleared while still seeing tpacket_rcv, causing __packet_rcv_has_room() to dereference stale or NULL ring storage.
Move the existing receive hook assignment into the same sk_receive_queue.lock section as the ring state update. Keep the assignment otherwise unchanged, including on TX ring reconfiguration, to avoid adding behavior changes that are not required for the fix.
Serialize packet_recvmsg() pressure clearing with the same queue lock only after PACKET_SOCK_PRESSURE has been observed. If the flag is clear and the socket has moved away from tpacket_rcv, packet_set_ring() has already detached the socket and waited for synchronize_net(), so no new packet input can set the flag again.
packet_poll() already holds sk_receive_queue.lock, so it uses the new unlocked helper directly.
Which versions are affected by CVE-2026-74666?
How do I fix CVE-2026-74666?
Apply the vendor's patch.
Is CVE-2026-74666 being exploited?
There is no known exploitation of CVE-2026-74666 in the wild and no public exploit code.
Sources
Also known as AZL-97343, BELL-CVE-2026-74666, DEBIAN-CVE-2026-74666, GHSA-qv67-9r8f-5pqx, UBUNTU-CVE-2026-74666.