---
title: "CVE-2026-56104: Chainlit contains a session hijacking vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-56104/
description: "CVE-2026-56104 (chainlit (PyPI)): Chainlit before 2.10.1 contains a session hijacking vulnerability that allows unauthenticated attackers to restore and…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-06-22
date_modified: 2026-10-08
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-56104"
kev: false
cvss: 8.8
epss: 0.00417
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-56104: Chainlit contains a session hijacking vulnerability

**Signal:** Normal patch cycle. No exploitation signal; fix it in your next routine update if you are affected. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4% , percentile 35: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 35% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes chainlit (PyPI) < 2.10.1, fixed in 2.10.1 . Check your lockfile, including transitive dependencies.

## What it is

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 restoreexistingsession 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

- PyPI `chainlit` < 2.10.1 → fixed: 2.10.1

## Affected products (CVE record)

- Chainlit chainlit: < 2.10.1

## Severity

- VulnCheck CVSS 4.0: 8.8 `CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N`
- VulnCheck CVSS 3.1: 8.2 `CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 4.0: 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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.42% probability of exploitation activity in the next 30 days; percentile 35.

## Sources

- [Release Notes](https://github.com/Chainlit/chainlit/releases/tag/2.10.1)
- [Patch Commit](https://github.com/Chainlit/chainlit/commit/5effb664f1e0af4a4f0a42fe63ea979676039a7f)
- [GitHub Advisory GHSA-c39v-8hrw-h448](https://github.com/advisories/GHSA-c39v-8hrw-h448)
- [CVE.org record CVE-2026-56104](https://www.cve.org/CVERecord?id=CVE-2026-56104)
- [NVD entry CVE-2026-56104](https://nvd.nist.gov/vuln/detail/CVE-2026-56104)
- [Pull Request](https://github.com/Chainlit/chainlit/pull/2857)
- [vulncheck.com](https://www.vulncheck.com/advisories/chainlit-session-hijacking-via-websocket-session-restoration)

---
Source page: https://erroneo.us/security/cve/CVE-2026-56104/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt