CVE-2026-6608 lm-sys fastchat Arena Side-by-Side View add_text control flow
Attackers can exploit incorrect control flow in the Arena Side-by-Side View handler to manipulate application logic.
- 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-2026-6608?
CVE-2026-6608 is a medium-severity vulnerability in lm-sys fastchat, published on 20 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-670
Which versions are affected by CVE-2026-6608?
3 open source packages ship an affected version, including fschat.
| 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 |
How do I fix CVE-2026-6608?
No fix has been published for CVE-2026-6608 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-6608 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6608 exists.
Sources
Also known as GHSA-f3q6-69f3-vwch, PYSEC-2026-2485.