---
id: "CVE-2026-98556"
kind: "vulnerability"
aliases: ["CVE-2026-98556"]
title: "Linux gve driver: out-of-range TSO MSS can make the device send malformed packets"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["google-cloud", "gve", "gvnic", "infrastructure", "linux-kernel"]
not_affected_if: ["no-gve-hardware"]
published_at: "2026-10-18T16:17:07+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:26+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98556", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux gve driver: out-of-range TSO MSS can make the device send malformed packets

The Google gve network driver in the Linux kernel does not reject TSO packets whose segment size exceeds what the device supports, so a crafted gso_size becomes a zero MSS in the hardware descriptor. The sources describe the packet mangling but do not state a confirmed code execution or data exposure impact.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update the Linux kernel to a release that includes the upstream gve fix rejecting out-of-range TSO MSS values (exact version not given in the sources).

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98556

## From the sources

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 regardless of the MTU, so falling back to software
segmentation would give the device non TSO packets bigger than the
9728 bytes it supports.

Note that the device can still be given oversized non TSO packets when
the stack segments in software for other reasons, for instance after
TSO has been disabled with ethtool. This is a generic issue, because
the MTU check is skipped for GSO packets in the forwarding path, and
is addressed separately.

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