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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact Low

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Chainlit chainlit unaffected
Version Status Constraints
0 affected ≤ 2.12.0

No data.

No data.

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Project Subscriptions

Vendors Products
Chainlit Subscribe
Chainlit Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

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

Wed, 09 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Wed, 09 Sep 2026 13:45:00 +0000

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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-09-09T14:49:36.459Z

Reserved: 2026-09-04T22:51:17.817Z

Link: CVE-2026-86099

cve-icon Vulnrichment

Updated: 2026-09-09T14:47:39.625Z

cve-icon NVD

Status : Received

Published: 2026-09-09T14:17:20.387

Modified: 2026-09-09T15:17:12.453

Link: CVE-2026-86099

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses