FastChat Denial of Service vulnerability
A Denial of Service (DoS) vulnerability exists in the file upload feature of lm-sys/fastchat version 0.2.36. The vulnerability is due to improper handling of form-data with a large filename in the file upload request. An attacker can exploit this by sending a payload with an excessively large filename, causing the server to become overwhelmed and unavailable to legitimate users.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | fschat | <= 0.2.36 | no fix |
References
- CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- Python (PyPI)
- Package
fschat- Disclosed
- 20.03.2025
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1395 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-79rp-v9rm-gxm8 - CC BY 4.0
Vulnerability history: fschat
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 03.2025 04.2026
- Without a fix
- 7
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 3
Disclosures per year
- 2025: 5
- 2026: 2
-
FastChat Denial of Service vulnerability this entry
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.