Cloudanix VulnDB

CVE-2026-98556

None

CVSS

—

EPSS

0.2%

Published

Oct 18, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A Linux network driver could receive unusual data packets from virtual machines that it was not prepared to handle, which might cause network slowdowns or errors until the software is updated.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Low
Impact
Other
Component
OS kernel
Class
Improper Input Validation
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

The gve driver fails to validate gso_size against the device's 9728-byte MSS limit in gve_prep_tso(), allowing values up to 16384 that are truncated to zero in the 14-bit TSO context descriptor; checks in gve_features_check_dqo() and is_skb_forwardable() also do not enforce the bound for forwarded or non-locally generated GSO packets.

Why it matters to the business

Systems using the gve network driver in virtualized or containerized environments risk network transmission failures, packet drops, or device instability when handling forwarded traffic, increasing operational overhead until patched kernels are deployed.

How an attack unfolds

An attacker generates or forwards a TSO packet with an out-of-range gso_size via a tap interface or packet socket; the packet bypasses MTU and GSO size checks in the forwarding path, reaches gve_tx_fill_tso_ctx_desc(), and produces an invalid descriptor that the device cannot process correctly.

How to fix it

Apply the upstream kernel patch that adds explicit rejection in gve_prep_tso() and preserves GSO bits only for valid sizes in gve_features_check_dqo(); rebuild and deploy the updated kernel image on affected hosts.

How to confirm the fix worked

Confirm the fix is present by inspecting the gve driver source for the added bounds check and gso_size validation logic, then test with synthetic packets containing gso_size values above 9728 to verify they are dropped before descriptor creation.

Typical attack path

  1. Craft or obtain a virtio_net_hdr with gso_size > 9728
  2. Inject via tap device or raw packet socket into a guest or forwarding path
  3. Bypass L2 forwarding and gso_features_check() MTU/GSO bounds
  4. Enter gve_prep_tso() and gve_tx_fill_tso_ctx_desc() with unvalidated value
  5. Trigger device malfunction or fallback segmentation failure

How to detect it

Review system and kernel logs for gve driver warnings or TSO-related errors during packet processing; examine network traces for GSO packets with unusually large gso_size values originating from tap or packet-socket paths.

What your security team should do

  • Prioritize kernel updates containing the gve TSO validation fix within the next maintenance window
  • Audit environments using gve for high-volume packet forwarding or tap-based guests
  • Temporarily disable TSO via ethtool on gve interfaces if immediate patching is not feasible
  • Monitor upstream stable kernel releases for the merged change

The record

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.

Affected packages

Ecosystem Package Introduced Fixed