CVE-2026-86099CWE-22path-traversal

CVE-2026-86099

High · published September 9, 2026

CVSS v3.1
8.2
EPSS
1%
Percentile
47.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
8.2 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
CVSS v4.0
8.8 · 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
EPSS
0.00598 · 47.9th percentile
Weakness
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Published
2026-09-09T18:17Z
References (5)
https://github.com/Chainlit/chainlit · [email protected]https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/session.py · [email protected]https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/socket.py · [email protected]https://pypi.org/project/chainlit/ · [email protected]https://www.vulncheck.com/advisories/chainlit-through-2.12.0-path-traversal-via-socket-io-sessionid · [email protected]
EPSS history
Timeline
  • 11 SEP 03:19Z
    EPSS moved — → 0%
    epss
  • 09 SEP 13:31Z
    Chainlit through 2.12.0 Path Traversal via socket.io sessionId
    cvelistv5