CVE-2026-98556
Received Received - Intake

Out-of-Range MSS in GVE DQO Driver

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

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.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98556
EUVD
EUVD-2026-103601

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
Linux Linux a57e5de476be0b4b7f42beb6a21c19ad9c577aa3
Linux Linux a57e5de476be0b4b7f42beb6a21c19ad9c577aa3
Linux Linux a57e5de476be0b4b7f42beb6a21c19ad9c577aa3
Linux Linux 5.14

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the gve network driver failing to enforce a maximum segment size (MSS) of 9728 bytes for TCP Segmentation Offload (TSO) packets. Attackers can exploit this by sending packets with an arbitrary gso_size, which may be converted to an invalid MSS value (e.g., zero) when processed by the driver. This could lead to improper packet handling or crashes.

Detection Guidance

This vulnerability affects the Linux kernel's gve driver for Google Virtio NICs. Detection requires checking if the system uses the vulnerable gve driver and inspecting network traffic for TSO packets with MSS values outside the expected range. No specific commands are provided in the context to detect this issue.

Impact Analysis

If you use a Linux system with the gve driver, an attacker on your network could send specially crafted packets to cause denial-of-service conditions, system crashes, or potential remote code execution. Systems acting as network gateways or with untrusted users may be at higher risk.

Mitigation Strategies

Update the Linux kernel to a patched version that includes the fix for CVE-2026-98556. If updating is not immediately possible, disable TSO (TCP Segmentation Offload) on the affected interface using ethtool: ethtool -K <interface> tso off. Monitor network traffic for signs of exploitation.

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