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Vulnerability · Published Apr 20, 2026 · Assigned by VulDB

CVE-2026-6608lm-sys fastchat Arena Side-by-Side View add_text control flow

Medium 5.3

In plain English

A medium-severity security flaw in fastchat from lm-sys. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities).

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.3%top 76.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

A vulnerability was detected in lm-sys fastchat up to 0.2.36. Impacted is the function add_text of the component Arena Side-by-Side View Handler. The manipulation results in incorrect control flow. The attack can be launched remotely. The exploit is now public and may be used. The root cause was fixed in commit 34eca62 for gradio_block_arena_named.py, but three other files were missed.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPIfschatno fix listedGHSA-f3q6-69f3-vwch
PyPIfschatno fix listedPYSEC-2026-2485

Affected products (as reported)

VendorProductVersions
lm-sys fastchat 0.2.00.2.10.2.20.2.30.2.40.2.50.2.60.2.7

Weakness: CWE-670 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:X/RC:R

References