FastChat Server-Side Request Forgery vulnerability

The SSRF vulnerability in fastchat allows an attacker to craft malicious requests that the server will execute on its behalf. A primary concern is the potential to access AWS metadata credentials if the server is deployed within an AWS environment. This could grant the attacker unauthorized access to AWS resources, including EC2 instances, S3 buckets, and other cloud services. Beyond AWS, the attacker could potentially access other internal services and databases that the server has access to, leading to data breaches and system compromise. The blast radius extends to any internal resources accessible by the fastchat server, making it a significant security risk.

Organizations deploying fastchat within AWS environments are particularly at risk due to the potential for credential theft. Shared hosting environments where multiple users share the same server instance are also vulnerable, as an attacker could potentially exploit the vulnerability to access resources belonging to other users. Any deployment relying on fastchat for internal communication or data processing is potentially at risk.

• python / server:

# Check for vulnerable versions
python -c 'import fastchat; print(fastchat.__version__)'

• generic web:

# Attempt to trigger SSRF by requesting an internal resource
curl http://<fastchat_server>/.well-known/server-status

• generic web:

# Check response headers for unusual origins
curl -I http://<fastchat_server> | grep 'Origin:'

1. 2025-03-20Disclosure

   disclosure

1. Reserviert2024-12-09
2. Veröffentlicht2025-03-20
3. Geändert2025-03-21
4. EPSS aktualisiert2026-04-02

The primary mitigation for CVE-2024-12376 is to upgrade to a patched version of fastchat. lm-sys should release a fix addressing the input validation issue. Until a patch is available, consider implementing a Web Application Firewall (WAF) to filter out malicious requests that attempt to exploit the SSRF vulnerability. Restrict network access to the fastchat server to only necessary ports and IP addresses. Regularly review and audit the server's configuration to ensure it adheres to security best practices. After upgrade, confirm by attempting a request to an internal resource and verifying that it is denied.