CVE-2026-98556

/// Technical description

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

gve: DQO: reject TSO packets with an out of range MSS

gve_prep_tso() notes that the device requires the MSS to be <= 9728,

but does not enforce it, assuming the 9K MTU enforced by the hypervisor

and the 64KB limit on TSO sizes are enough.

This does not hold for packets that were not generated locally.

A guest behind a tap, or any packet socket user, can provide an

arbitrary gso_size in virtio_net_hdr. Layer 2 forwarding does not check

the MTU for GSO packets (is_skb_forwardable()), and gso_features_check()

only bounds skb->len and gso_segs, never gso_size.

Such a packet reaches gve_tx_fill_tso_ctx_desc(), which puts gso_size

into the mss field of the TSO context descriptor. This field is 14 bits

wide, so a gso_size of 16384 is silently turned into an MSS of zero.

Drop these packets from gve_prep_tso(), and make sure that

gve_features_check_dqo() leaves their GSO bits alone: skb_segment()

splits at gso_size regardl

/// 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