vLLM: DoS via unbounded chat_template Jinja2 rendering exhausts the renderer thread pool

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-115911
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-26 17:17:18 UTC
Updated2026-10-26 18:34:17 UTC
DescriptionvLLM is an inference and serving engine for large language models. From 0.19.0 until 0.32.0, authenticated callers can supply a request chat template when no server-side --chat-template is configured, or a malicious model repository can provide a template that is compiled and rendered by tokenizer.apply_chat_template() without a wall-clock timeout, output-size limit, or iteration bound. Rendering runs in a ThreadPoolExecutor with one worker by default, so a nonterminating render can block /v1/responses and other chat-template users after the request ends, while an output-expanding render can exhaust server memory. Harmony models are not affected because they do not use this Jinja path. This issue is fixed in version 0.32.0.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-400 | CWE-770 | CWE-834 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling | CWE-834 CWE-834: Excessive Iteration

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Vllm-project Vllm affected >= 0.19.0, < 0.32.0 Not specified

References

ReferenceSourceLinkTags
github.com/vllm-project/vllm/releases/tag/v0.32.0 [email protected] github.com
github.com/vllm-project/vllm/security/advisories/GHSA-542m-9234-8gvf [email protected] github.com
github.com/vllm-project/vllm/commit/cff08b461e086523cee8bba5bd3c66d30262... [email protected] github.com
github.com/vllm-project/vllm/pull/50300 [email protected] github.com
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