CVE-2026-86099

HIGH 8.2

Chainlit through 2.12.0 Path Traversal via socket.io sessionId

CVSS Score

8.2

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-22
Vendor	chainlit
Product	chainlit
Published	Sep 9, 2026
Last Updated	Sep 9, 2026

Stay Ahead of the Next One

Get instant alerts for chainlit chainlit

Be the first to know when new high vulnerabilities affecting chainlit chainlit are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

High

Affected Versions

Chainlit / chainlit

0 ≤ 2.12.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/Chainlit/chainlit github.com: https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/session.py github.com: https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/socket.py pypi.org: https://pypi.org/project/chainlit/ vulncheck.com: https://www.vulncheck.com/advisories/chainlit-through-2.12.0-path-traversal-via-socket-io-sessionid

Credits

mil4n