CVE-2026-86099

Chainlit through 2.12.0 Path Traversal via socket.io sessionId

Published Sep 9, 2026 CVSS 4.0 · 8.8 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Chainlit through 2.12.0 Path Traversal via socket.io sessionId
First Time appeared Chainlit
Chainlit chainlit
Weaknesses CWE-22
CPEs cpe:2.3:a:chainlit:chainlit:*:*:*:*:*:*:*:*
Vendors & Products Chainlit
Chainlit chainlit
References
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H'}

cvssV4_0

{'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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Sep 9, 2026, 2:49 PM
Reserved
Sep 4, 2026, 10:51 PM
Status
Deferred
Published
Sep 9, 2026, 2:17 PM
Modified
Sep 9, 2026, 8:20 PM