CVE-2026-86099

high

Chainlit through 2.12.0 fails to validate the client-supplied socket.io sessionId parameter, allowing unauthenticated attackers to traverse filesystem paths by…

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.

CVSS

8.2

8.2 (CVSS v3.1)

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

Severity source: NVD CVSS v3.1 (disclosure@vulncheck.com)

Timeline (UTC)

Published: 2026-09-09 14:17

Modified: 2026-09-09 20:20

NVD status: Deferred

Last synced 2 days ago

Verified against the source API 2026-10-27 06:52 UTC

Exploitation

Not listed in CISA KEV (as of last catalog sync)

Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

Not reported by the source (unknown — not "none").

Weakness classification (CWE)

CWE-22

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

No vendor advisory or patch reference tagged by NVD. Check the references below.

References

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

Data sources

NVD CVE API 2.0 — fetched 2026-10-27 06:52 UTC · record ↗

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