# CVE-2026-56104 — chainlit

> As of 2026-06-23, CVE-2026-56104 is a HIGH-severity vulnerability in chainlit, CVSS v3.1 7.4, EPSS 0.2% (21.2th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-56104 as of 2026-06-23; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-06-23

## 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](https://intel.threadlinqs.com/cwe/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 2026-06-24.

**Vendor advisory and patch**

- [github.com — release notes](https://github.com/Chainlit/chainlit/releases/tag/2.10.1)
- [github.com — patch](https://github.com/Chainlit/chainlit/commit/5effb664f1e0af4a4f0a42fe63ea979676039a7f)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/chainlit-session-hijacking-via-websocket-session-restoration)

**Issue tracking and product pages**

- [github.com — issue tracking](https://github.com/Chainlit/chainlit/pull/2857)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-56104
Full detection coverage and IOCs for threats exploiting CVE-2026-56104 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp