---
id: CVE-2026-6607
aliases:
  - GHSA-5h65-jx66-j7p5
  - PYSEC-2026-2484
title: >-
  FastChat has Denial of Service Through Blocking Event Loop in Model Workers
  (Incomplete Fix for ff66426)
summary: >-
  FastChat has Denial of Service Through Blocking Event Loop in Model Workers
  (Incomplete Fix for ff66426)
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
vendor: fschat
product: fschat
ecosystem: pip
affected:
  - fschat <= 0.2.26
published: '2026-04-20'
updated: '2026-07-13'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-5h65-jx66-j7p5'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-6607'
  - url: 'https://github.com/lm-sys/FastChat/issues/3833'
  - url: 'https://github.com/lm-sys/FastChat/pull/3835'
  - url: >-
      https://github.com/lm-sys/FastChat/commit/c9e84b89c91d45191dc24466888de526fa04cf33
  - url: 'https://gist.github.com/YLChen-007/87216a2d97a882d619e11dc67cd473b5'
  - url: 'https://github.com/lm-sys/FastChat'
  - url: 'https://vuldb.com/submit/792227'
  - url: 'https://vuldb.com/vuln/358242'
  - url: 'https://vuldb.com/vuln/358242/cti'
tags:
  - osv
  - pip
epss: 0.00741
epssPercentile: 0.52637
ingestedAt: '2026-07-13T18:57:53.274Z'
---

## Overview

A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py but missed other entry points.

## Affected packages

- `fschat <= 0.2.26`

## Remediation

Refer to the advisory for the patched release.