# CVE-2026-98556: gve: DQO: reject TSO packets with an out of range MSS

> A local attacker can cause a denial of service in the gve network driver by sending crafted packets with invalid MSS values.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108581, BELL-CVE-2026-98556, DEBIAN-CVE-2026-98556, GHSA-jwgx-gfj4-hvfm, UBUNTU-CVE-2026-98556

## What is CVE-2026-98556?

CVE-2026-98556 is a denial of service vulnerability in Linux, published on 18 Oct 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:

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.

## Which versions are affected by CVE-2026-98556?


## How do I fix CVE-2026-98556?

Apply the vendor's patch.

## Is CVE-2026-98556 being exploited?

There is no known exploitation of CVE-2026-98556 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98556 and fix it if it is affected.

What it is: CVE-2026-98556 is a denial of service vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98556 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98556/ (Markdown: https://insights.sbomify.com/CVE-2026-98556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98556
- OSV: https://osv.dev/vulnerability/CVE-2026-98556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98556/
Summaries are generated and may contain mistakes; the official description above is the record.