What is 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.
The record classifies CVE-2026-56104 under weakness class CWE-862. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 105 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.4 — HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS v4.0 base score
- 9.1
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N - EPSS (FIRST)
- 0.2% probability of exploitation in the next 30 days, higher than 21.2% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-06-22, last modified 2026-06-23
Is CVE-2026-56104 being exploited?
It currently carries a trending score of 35 in the Threadlinqs vulnerability feed.
Affected products and versions
- Chainlit: chainlit
How to fix CVE-2026-56104
No vendor patch reference has been recorded for CVE-2026-56104 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-56104
No threat campaign in the Threadlinqs corpus currently references CVE-2026-56104, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, GitHub Security Advisories, FIRST EPSS. Last verified by Threadlinqs on .