# CVE-2026-46273: ibmveth: Disable GSO for packets with small MSS

> A flaw in the Linux kernel ibmveth driver allows remote attackers to freeze network adapters by sending packets with small MSS values, causing a denial of service.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Jun 2026
- **Updated:** 7 Aug 2026
- **Also known as:** AZL-89345, BELL-CVE-2026-46273, DEBIAN-CVE-2026-46273, GHSA-c3jf-v88j-7gvj, ROOT-OS-DEBIAN-11-CVE-2026-46273, ROOT-OS-DEBIAN-12-CVE-2026-46273, ROOT-OS-UBUNTU-2204-CVE-2026-46273, ROOT-OS-UBUNTU-2404-CVE-2026-46273, UBUNTU-CVE-2026-46273

## What is CVE-2026-46273?

CVE-2026-46273 is a high-severity denial of service vulnerability in Linux kernel, published on 3 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ibmveth: Disable GSO for packets with small MSS

Some physical adapters on Power systems do not support segmentation
offload when the MSS is less than 224 bytes. Attempting to send such
packets causes the adapter to freeze, stopping all traffic until
manually reset.

Implement ndo_features_check to disable GSO for packets with small MSS
values. The network stack will perform software segmentation instead.

The 224-byte minimum matches ibmvnic
commit <f10b09ef687f> ("ibmvnic: Enforce stronger sanity checks
on GSO packets")
which uses the same physical adapters in SEA configurations.

The issue occurs specifically when the hardware attempts to perform
segmentation (gso_segs > 1) with a small MSS. Single-segment GSO packets
(gso_segs == 1) do not trigger the problematic LSO code path and are
transmitted normally without segmentation.

Add an ndo_features_check callback to disable GSO when MSS < 224 bytes.
Also call vlan_features_check() to ensure proper handling of VLAN packets,
particularly QinQ (802.1ad) configurations where the hardware parser may
not support certain offload features.

Validated using iptables to force small MSS values. Without the fix,
the adapter freezes. With the fix, packets are segmented in software
and transmission succeeds. Comprehensive regression testing completedd
(MSS tests, performance, stability).

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-46273?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46273?

Apply the vendor's patch.

## Is CVE-2026-46273 being exploited?

There is no known exploitation of CVE-2026-46273 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46273 and fix it if it is affected.

What it is: CVE-2026-46273 is a high-severity denial of service vulnerability in Linux kernel, published on 3 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-46273 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-46273/ (Markdown: https://insights.sbomify.com/CVE-2026-46273/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46273
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46273
- OSV: https://osv.dev/vulnerability/CVE-2026-46273

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46273/
Summaries are generated and may contain mistakes; the official description above is the record.