CVE-2026-86099: Chainlit through 2.12.0 Path Traversal via socket.io sessionId
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.
Affected Software
Event History
Frequently Asked Questions
Does exploiting this issue require authentication or user interaction?
No. The vulnerability is exploitable by an unauthenticated attacker over the network and does not require user interaction.
What level of access does an attacker need to cause damage?
An attacker needs to submit a crafted socket.io sessionId value containing absolute paths or relative path traversal sequences. The affected service process must have filesystem permissions to the directories the attacker targets.
Which versions are identified as affected?
Chainlit through version 2.12.0 is identified as affected.