CVE-2026-86099
High
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.
SeverityHigh
CVSS8.2
Exploit probability—
ProductChainlit
PublishedSep 9, 2026
First seenSep 9, 2026
Weakness typeCWE-22Path traversal
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Chainlit chainlit | v ≤ 2.12.0 | — |
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