CVE-2024-10907 Denial of Service (DoS) via Multipart Boundary in lm-sys/fastchat

High 7.5 Published 20 Mar 2025 Updated 15 Oct 2025

Unauthenticated attackers can cause a denial of service in FastChat by sending malformed multipart requests that trigger an infinite loop.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2024-10907?

CVE-2024-10907 is a high-severity denial of service vulnerability in lm-sys/fastchat, published on 20 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In lm-sys/fastchat Release v0.2.36, the server fails to handle excessive characters appended to the end of multipart boundaries. This flaw can be exploited by sending malformed multipart requests with arbitrary characters at the end of the boundary. Each extra character is processed in an infinite loop, leading to excessive resource consumption and a complete denial of service (DoS) for all users. The vulnerability is unauthenticated, meaning no user login or interaction is required for an attacker to exploit this issue.

Weakness: CWE-835

Which versions are affected by CVE-2024-10907?

3 open source packages ship an affected version, including fschat. It affects 1 product.

Package	Affected	Fixed in
`fschat` PyPI	All versions to `0.2.36`	None
`fschat` PyPI	All versions to `0.2.36`	None
`fschat` PyPI	All versions to `0.2.36`	None

Products include Lm-Sys Fastchat.

How do I fix CVE-2024-10907?

No fix has been published for CVE-2024-10907 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2024-10907 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-10907 exists.

Sources

Also known as GHSA-qg86-f892-m4hj, PYSEC-2026-1398.