CVE-2026-80725

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

net: gro: properly validate BIG TCP aggregation criteria

When GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB),

BIG TCP should only be permitted for plain IPv4 TCP and plain IPv6 TCP

(with sufficient MAC header room to insert the temporary HBH jumbo header).

However, commit b1a78b9b9886 ("net: add support for ipv4 big tcp")

loosened the check in skb_gro_receive(), leading to several issues:

1. skb_gro_receive() checked skb_headroom(p) instead of the actual space

before the MAC header (p->mac_header). Because skb_headroom(p) includes

mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check

with p->mac_header < 8 bytes. When ipv6_gro_complete() inserts the

temporary HBH jumbo header, the memmove() starts before skb->head,

causing an out-of-bounds write and wrapping skb->mac_header.

2. It allowed non-IP protocols such as software VLAN (ETH_P_8021Q /

ETH_P_8021AD) to

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References