CVE-2026-56104

High

Description

Chainlit before 2.10.1 contains a session hijacking vulnerability that allows unauthenticated attackers to restore and inherit authenticated user sessions by presenting a valid sessionId during WebSocket session restoration without ownership verification. Attackers can exploit the restore_existing_session path to assume a victim's permissions and roles, enabling unauthorized invocation of tools and access to data restricted to the authenticated victim.

SeverityHigh

CVSS8.2

Exploit probability—

ProductChainlit

PublishedJun 22, 2026

First seenJun 22, 2026

Weakness typeCWE-862Missing authorization

How to fix

Update

chainlit2.10.1 or later

Patches

github.com/Chainlit/chainlit/commit/5effb664f1e0af4a4f0a42fe63ea979676039a7f

Vendor advisories

github.com/Chainlit/chainlit/releases/tag/2.10.1

Affected products

Product	Affected versions	Fixed in
chainlitPyPI	v < 2.10.1	2.10.1

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