CVE-2026-86099 Chainlit through 2.12.0 Path Traversal via socket.io sessionId
Unauthenticated attackers can exploit path traversal in Chainlit to delete arbitrary directories, causing data loss and service disruption.
- 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-2026-86099?
CVE-2026-86099 is a high-severity path traversal vulnerability in chainlit, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Chainlit through 2.12.0 fails to validate the client-supplied socket.io sessionId parameter, allowing unauthenticated attackers to traverse filesystem paths by injecting absolute or relative path sequences. Attackers can craft malicious sessionId values that escape the upload directory and recursively delete arbitrary directories accessible to the service process.
Weakness: CWE-22
Which versions are affected by CVE-2026-86099?
How do I fix CVE-2026-86099?
No fix has been published for CVE-2026-86099 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-86099 being exploited?
There is no known exploitation of CVE-2026-86099 in the wild and no public exploit code.
Sources
Also known as GHSA-wf68-h55h-fvxv.