Path Traversal Vulnerability in Chainlit from Vendor Chainlit
CVE-2026-86099

8.8HIGH

Key Information:

Vendor

Chainlit

Status
Chainlit
Vendor
CVE Published:
9 September 2026

What is CVE-2026-86099?

Chainlit versions up to 2.12.0 are susceptible to a path traversal vulnerability due to insufficient validation of the client-supplied socket.io sessionId parameter. Attackers can exploit this weakness by injecting crafted sessionId values, which enables them to manipulate filesystem paths. This could lead to the unauthorized deletion of arbitrary directories outside the intended upload directory, posing significant risks to the integrity of the service and the data it handles.

Affected Version(s)

chainlit 0 <= 2.12.0

References

https://github.com/Chainlit/chainlit
product
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/...
technical-description
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/...
technical-description

CVSS V4

Score:
8.8
Severity:
HIGH
Confidentiality:
None
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

mil4n
.