CVE-2026-86099

high

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.

References

https://www.vulncheck.com/advisories/chainlit-through-2.12.0-path-traversal-via-socket-io-sessionid

https://pypi.org/project/chainlit/

https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/socket.py

https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/session.py

https://github.com/Chainlit/chainlit

Details

Source: Mitre, NVD

Published: 2026-09-09

Updated: 2026-09-09

Risk Information

CVSS v2

Base Score: 8.5

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:C

Severity: High

CVSS v3

Base Score: 8.2

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Severity: High

CVSS v4

Base Score: 8.8

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N

Severity: High

EPSS

EPSS: 0.00394