PYSEC-2026-4186: vllm-project vLLM Gemma4UnifiedParser gemma4.rs denial of service

Q: Which deployments are exposed?

vLLM deployments using the Gemma4UnifiedParser are affected if they run a version up to 0.26.0. The issue can be triggered remotely and does not require authentication or user interaction.

Q: What does an attacker need to do to exploit this issue?

An attacker needs to send a manipulation that reaches the Gemma4UnifiedParser code in rust/src/parser/src/unified/gemma4.rs. The available data does not further specify the crafted input or request conditions.

Q: Is exploitation practical?

Yes. An exploit has been published, and the vulnerability is rated as low attack complexity with network reachability.

Q: What should teams do to remediate it?

Upgrade vLLM to version 0.29.1rc0 or later. The stated fix is patch 3439bad37e68ba9755a46f4f6b44a4aeaf1f60a9.

Published Sep 30, 2026

Updated

A flaw has been found in vllm-project vLLM up to 0.26.0. This vulnerability affects unknown code of the file rust/src/parser/src/unified/gemma4.rs of the component Gemma4UnifiedParser. Executing a manipulation can lead to denial of service. The attack may be launched remotely. The exploit has been published and may be used. Upgrading to version 0.29.1rc0 is able to resolve this issue. This patch is called 3439bad37e68ba9755a46f4f6b44a4aeaf1f60a9. Upgrading the affected component is advised.

Affected Software

1 affected component

vllm-project vllm<=0.26.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade vllm-project/vLLM to a version that resolves this vulnerability.
Fixed in 0.29.1rc0Patch 3439bad37e68ba9755a46f4f6b44a4aeaf1f60a9

Event History

Sep 30, 2026

CVE Published

via OSV·04:45 PM

Data Sourced

via OSV·04:45 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are exposed?

vLLM deployments using the Gemma4UnifiedParser are affected if they run a version up to 0.26.0. The issue can be triggered remotely and does not require authentication or user interaction.

What does an attacker need to do to exploit this issue?

An attacker needs to send a manipulation that reaches the Gemma4UnifiedParser code in rust/src/parser/src/unified/gemma4.rs. The available data does not further specify the crafted input or request conditions.

Is exploitation practical?

Yes. An exploit has been published, and the vulnerability is rated as low attack complexity with network reachability.

What should teams do to remediate it?

Upgrade vLLM to version 0.29.1rc0 or later. The stated fix is patch 3439bad37e68ba9755a46f4f6b44a4aeaf1f60a9.

PYSEC-2026-4186: vllm-project vLLM Gemma4UnifiedParser gemma4.rs denial of service

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are exposed?

What does an attacker need to do to exploit this issue?

Is exploitation practical?

What should teams do to remediate it?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed?

What does an attacker need to do to exploit this issue?

Is exploitation practical?

What should teams do to remediate it?