CVE-2026-74668 packet: use consistent hard_header_len in TX_RING send path
A race condition in the Linux kernel packet socket TX path can cause memory corruption or crashes due to inconsistent header length usage during concurrent reconfiguration.
- 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-2026-74668?
CVE-2026-74668 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: use consistent hard_header_len in TX_RING send path
tpacket_snd() reads dev->hard_header_len independently for skb allocation and header construction in tpacket_fill_skb(). Concurrent netdevice reconfiguration can therefore make the reserved headroom smaller than the amount later pushed, or make copylen - hard_header_len negative.
Snapshot hard_header_len once before processing ring frames and use it for the frame limit, headroom allocation, copy length, and skb construction. Pass the snapshot to tpacket_fill_skb().
The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here.
Which versions are affected by CVE-2026-74668?
How do I fix CVE-2026-74668?
Apply the vendor's patch.
Is CVE-2026-74668 being exploited?
There is no known exploitation of CVE-2026-74668 in the wild and no public exploit code.
Sources
Also known as AZL-97371, BELL-CVE-2026-74668, DEBIAN-CVE-2026-74668, GHSA-j5cf-5xp4-r57f, UBUNTU-CVE-2026-74668.