Auth bypass in Chainlit
CVE-2026-56104
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (33.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 33.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Chainlit — versions 0
Weakness classification (CWE)
References
- github.com/Chainlit/chainlit/releases/tag/2.10.1 (release-notes)
- github.com/Chainlit/chainlit/pull/2857 (issue-tracking)
- github.com/Chainlit/chainlit/commit/5effb664f1e0af4a4f0a42fe63ea979676039a7f (patch)
- www.vulncheck.com/advisories/chainlit-session-hijacking-via-websocket-session-r… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-56104?
- CVE-2026-56104 is a high-severity vulnerability in Chainlit, classified under Missing Authorization. CVSS score: 8.2/10. Published 2026-06-22.
- How severe is CVE-2026-56104?
- High severity. CVSS v3 base score is 8.2 out of 10.