Control Flow Vulnerability in lm-sys FastChat Product
CVE-2026-6608

6.9MEDIUM

Key Information:

Vendor

Lm-sys

Status
Fastchat
Vendor
CVE Published:
20 April 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-6608?

A control flow vulnerability exists in the lm-sys FastChat application, specifically within the add_text function of the Arena Side-by-Side View Handler component, affecting all versions up to 0.2.36. This flaw allows remote attackers to manipulate the application, resulting in unexpected control flow. Although a fix has been applied to one file, other related files remain vulnerable, allowing for potential exploitation. Given the exploitation is now public, it's critical for users to be aware of the affected versions and apply any necessary updates.

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-2026-6608 - Proof of Concept

References

https://vuldb.com/vuln/358243
vdb-entrytechnical-description
https://vuldb.com/vuln/358243/cti
signaturepermissions-required
https://vuldb.com/submit/792228
third-party-advisory

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
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)
.