---
id: CVE-2025-62426
title: >-
  vllm: vLLM vulnerable to DoS via large Chat Completion or Tokenization
  requests with specially crafted `chat_template_kwargs` (CVE-2025-624…
summary: >-
  A vulnerability in vLLM allows an authenticated user to trigger unintended
  tokenization during chat template processing by supplying crafted
  chat_template_kwargs to the /v1/chat/completions or /tokenize endpoints. By
  forcing the server to …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: vendor
cwe: CWE-770
vendor: Red Hat
product: Red Hat Enterprise Linux AI (RHEL AI)
affected:
  - ai_inference_server
  - enterprise_linux_ai_rhel_ai
  - enterprise_linux_ai_rhel_ai 3
  - openshift_ai_rhoai
  - ai_inference_server 3.2
patched:
  - ai_inference_server 3.2
published: '2025-11-21'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T17:09:31+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-62426.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-62426.json
  - url: 'https://access.redhat.com/security/cve/CVE-2025-62426'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2416278'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2025-62426'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-62426'
  - url: >-
      https://github.com/vllm-project/vllm/blob/2a6dc67eb520ddb9c4138d8b35ed6fe6226997fb/vllm/entrypoints/chat_utils.py#L1602-L1610
  - url: >-
      https://github.com/vllm-project/vllm/blob/2a6dc67eb520ddb9c4138d8b35ed6fe6226997fb/vllm/entrypoints/openai/serving_engine.py#L809-L814
  - url: >-
      https://github.com/vllm-project/vllm/commit/3ada34f9cb4d1af763fdfa3b481862a93eb6bd2b
  - url: 'https://github.com/vllm-project/vllm/pull/27205'
  - url: >-
      https://github.com/vllm-project/vllm/security/advisories/GHSA-69j4-grxj-j64p
  - url: 'https://access.redhat.com/errata/RHSA-2026:3461'
  - url: 'https://access.redhat.com/errata/RHSA-2026:3462'
  - url: 'https://github.com/advisories/GHSA-69j4-grxj-j64p'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/vllm/PYSEC-2026-2012.yaml
  - url: 'https://github.com/vllm-project/vllm'
  - url: 'https://pypi.org/project/vllm'
tags:
  - csaf
  - vex
  - red-hat
  - osv
  - pip
epss: 0.00368
epssPercentile: 0.27962
aliases:
  - GHSA-69j4-grxj-j64p
  - PYSEC-2026-2012
ecosystem: pip
ingestedAt: '2026-07-08T18:25:46.322Z'
---

## Overview

A vulnerability in vLLM allows an authenticated user to trigger unintended tokenization during chat template processing by supplying crafted chat_template_kwargs to the /v1/chat/completions or /tokenize endpoints. By forcing the server to tokenize very large inputs, an attacker can block the API server’s event loop for extended periods, causing a denial of service and delaying all other requests.

## Vendor advisories

- **RHSA-2026:3461** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-02-27 · [advisory](https://access.redhat.com/errata/RHSA-2026:3461)
- **RHSA-2026:3462** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-02-27 · [advisory](https://access.redhat.com/errata/RHSA-2026:3462)
- **Red Hat VEX** · Moderate · affected: Red Hat AI Inference Server, Red Hat Enterprise Linux AI (RHEL AI), Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat AI Inference Server, Red Hat Enterprise Linux AI (RHEL AI), Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-62426.json)

**vllm: vLLM vulnerable to DoS via large Chat Completion or Tokenization requests with specially crafted `chat_template_kwargs`** — rated Moderate by Red Hat. Released 2025-11-21, updated 2026-09-21.

Affected:

- Red Hat AI Inference Server
- Red Hat Enterprise Linux AI (RHEL AI)
- Red Hat Enterprise Linux AI (RHEL AI) 3
- Red Hat OpenShift AI (RHOAI)

Fixed:

- Red Hat AI Inference Server 3.2

No fix planned:

- Red Hat AI Inference Server
- Red Hat Enterprise Linux AI (RHEL AI)
- Red Hat Enterprise Linux AI (RHEL AI) 3
- Red Hat OpenShift AI (RHOAI)

## Remediation

For more information visit https://access.redhat.com/errata/RHSA-2026:3461 https://access.redhat.com/errata/RHSA-2026:3461
For more information visit https://access.redhat.com/errata/RHSA-2026:3462 https://access.redhat.com/errata/RHSA-2026:3462

Workarounds / mitigations:

- No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.

## Package advisory (CVE-2025-62426)

Affected packages:

- `vllm >= 0.5.5, < 0.11.1`

Patched in:

- `vllm 0.11.1`

Source: https://osv.dev/vulnerability/GHSA-69j4-grxj-j64p