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

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

Which versions are affected by CVE-2026-46273?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-46273?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

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 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

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 and 3 more.