Vulnerability · Published Jun 22, 2026 · Assigned by VulnCheck

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

High 8.2

In plain English

A high-severity missing authorization in chainlit from Chainlit. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.2High

Exploit odds (30 days)0.4%top 63.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	chainlit	2.10.1	GHSA-c39v-8hrw-h448
PyPI	chainlit	2.10.1	PYSEC-2026-4028

Affected products (as reported)

Vendor	Product	Versions
Chainlit	chainlit	0 – before 2.10.1

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N

References

Release Notes release-notes
Pull Request issue-tracking
Patch Commit patch
https://www.vulncheck.com/advisories/chainlit-session-hijacking-via-websocket-session-restoration third-party-advisory