What’s Vulnerable › Vulnerabilities

CVE-2026-56104: Chainlit < 2.10.1 Session Hijacking via WebSocket Session Restoration

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-22 · updated 2026-10-08
• Weakness: CWE-862

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.

Affected products

• chainlit: before 2.10.1 — fixed in 2.10.1

How to fix

Upgrade to a fixed version: chainlit 2.10.1. Check the vendor advisory for mitigations.

References

• https://github.com/Chainlit/chainlit/commit/5effb664f1e0af4a4f0a42fe63ea979676039a7f
• https://github.com/Chainlit/chainlit/pull/2857
• https://github.com/Chainlit/chainlit/releases/tag/2.10.1
• https://www.vulncheck.com/advisories/chainlit-session-hijacking-via-websocket-session-restoration

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