CVE-2026-56104 Chainlit < 2.10.1 Session Hijacking via WebSocket Session Restoration
Unauthenticated attackers can hijack user sessions via WebSocket restoration, gaining unauthorized access to tools and data.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-56104?
CVE-2026-56104 is a high-severity authentication bypass vulnerability in chainlit, published on 22 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-862
Which versions are affected by CVE-2026-56104?
3 open source packages ship an affected version, including chainlit.
| Package | Affected | Fixed in |
|---|---|---|
chainlit PyPI | All versions | 2.10.1 |
chainlit PyPI | All versions | 2.10.1 |
chainlit PyPI | All versions | 2.10.1 |
How do I fix CVE-2026-56104?
Upgrade chainlit to 2.10.1 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-56104 being exploited?
There is no known exploitation of CVE-2026-56104 in the wild and no public exploit code.
Sources
Also known as GHSA-c39v-8hrw-h448, PYSEC-2026-4028.