CVE-2026-80742 af_packet: Don't send zero-byte data in tpacket_snd().
A local attacker can trigger a kernel warning and potential denial of service by sending zero-byte packets via TPACKET ring buffers.
- 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-2026-80742?
CVE-2026-80742 is a denial of service vulnerability in Linux, published on 3 Sep 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:
af_packet: Don't send zero-byte data in tpacket_snd().
syzbot reported a WARNING in __dev_queue_xmit() triggered via tpacket_snd():
skb_assert_len WARNING: at include/linux/skbuff.h:2753 skb_assert_len WARNING: at __dev_queue_xmit+0x21bc/0x4970 net/core/dev.c:4781
Call Trace: <TASK> dev_queue_xmit include/linux/netdevice.h:3448 [inline] packet_xmit+0x243/0x310 net/packet/af_packet.c:276 tpacket_snd net/packet/af_packet.c:2907 [inline] packet_sendmsg+0x28d6/0x4eb0 net/packet/af_packet.c:3134
When sending 0-byte packets via TPACKET ring buffer on devices with no hard header (e.g. dev->hard_header_len == 0), tpacket_fill_skb() populates an skb with skb->len == 0 and returns 0. tpacket_snd() then forwards this empty skb to packet_xmit(), causing __dev_queue_xmit() to hit skb_assert_len(skb).
Similar checks exist in packet_snd() via commit dc633700f00f ("net/af_packet: check len when min_header_len equals to 0") and in packet_sendmsg_spkt() via commit 6a341729fb31 ("af_packet: Don't send zero-byte data in packet_sendmsg_spkt().").
Return -EINVAL in tpacket_fill_skb() when skb->len is zero to reject zero-length packets in tpacket_snd().
Which versions are affected by CVE-2026-80742?
How do I fix CVE-2026-80742?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-80742 being exploited?
There is no known exploitation of CVE-2026-80742 in the wild and no public exploit code.
Sources
Also known as AZL-99036, BELL-CVE-2026-80742, DEBIAN-CVE-2026-80742, GHSA-66qw-vmh2-j2c2, UBUNTU-CVE-2026-80742.