# CVE-2026-80742: af\_packet: Don't send zero-byte data in tpacket\_snd().

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-09-03 · Updated: 2026-09-03

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/dde212f8622f5cb36223fff1ebd6e6f2a3dc61fe
- https://git.kernel.org/stable/c/80a702964467b998d254f16cc61c2c9a20540c9d
- https://git.kernel.org/stable/c/7521e691c7c4f2231634c95053281ac888d1f452
- https://git.kernel.org/stable/c/1fc70b3d513bafb16b17540178870ef46e81c0bb
- https://git.kernel.org/stable/c/3fa110f9e2ea96f567f2194c673c4bc327640111
- https://git.kernel.org/stable/c/98c5914d6b7bd4b4675535908e57dea31f1efd6a
- https://git.kernel.org/stable/c/f09ac5682f1bb67981fcb6ead4d3cfe439225876
- https://git.kernel.org/stable/c/6bcd76c134c55c697148acb5c0194e9666abdf84

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