Denial of Service Vulnerability in lm-sys FastChat by lm-sys
CVE-2026-6607

6.9MEDIUM

Key Information:

Vendor

Lm-sys

Status
Fastchat
Vendor
CVE Published:
20 April 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-6607?

A security issue has been identified in the lm-sys FastChat application, specifically affecting versions up to 0.2.36. This vulnerability is located in the api_generate function of the Worker API Endpoint, where improper handling can lead to excessive resource consumption. The attack can be executed remotely, and the exploit has already been made public. To mitigate the issue, a patch has been suggested, but while it addresses one method of exploitation in the base_model_worker.py file, other potential entry points may still remain unpatched. Users are encouraged to monitor updates from the vendor and apply available fixes to enhance their security posture.

Affected Version(s)

fastchat 0.2.0

fastchat 0.2.1

fastchat 0.2.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-6607 - Proof of Concept

References

https://vuldb.com/vuln/358242
vdb-entrytechnical-description
https://vuldb.com/vuln/358242/cti
signaturepermissions-required
https://vuldb.com/submit/792227
third-party-advisory

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Eric-f (VulDB User)
.