---
id: CVE-2026-120492
title: Chainlit 2.12.0 SSRF via Semicolon Path Segment in MCP allowed_urls
summary: >-
  Chainlit 2.12.0 contains a server-side request forgery vulnerability that
  allows unauthenticated attackers to bypass path-scoped MCP allowed_urls
  entries because validate_mcp_url does not reject the semicolon character.
  Attackers can sub…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N'
cvssSource: cna
cwe:
  - CWE-918
vendor: Chainlit
product: Chainlit
affected:
  - Chainlit 2.12.0
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-07T00:22:32.709220Z'
exploitAvailable: true
published: '2026-11-02'
updated: '2026-11-07'
sourceUpdated: '2026-11-07T00:22:59.156Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-120492'
references:
  - url: >-
      https://github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j
    label: GitHub Security Advisory (GHSA-hvfh-5mj3-5f3j)
  - url: >-
      https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L90-L177
  - url: >-
      https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L199-L208
  - url: >-
      https://www.vulncheck.com/advisories/chainlit-2.12.0-ssrf-via-semicolon-path-segment-in-mcp-allowed-urls
    label: >-
      VulnCheck Advisory: Chainlit 2.12.0 SSRF via Semicolon Path Segment in MCP
      allowed_urls
  - url: >-
      https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9
  - url: 'https://github.com/Chainlit/chainlit'
  - url: >-
      https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-002--ssrf-via-mcp-streamable-http--sse
  - url: 'https://github.com/Chainlit/chainlit/releases/tag/2.12.0'
  - url: 'https://pypi.org/project/chainlit'
  - url: 'https://github.com/advisories/GHSA-hvfh-5mj3-5f3j'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-45019'
tags:
  - cve.org
  - exploit-available
  - osv
  - pip
epss: 0.00221
epssPercentile: 0.12729
aliases:
  - GHSA-hvfh-5mj3-5f3j
  - CVE-2026-45019
  - PYSEC-2026-3811
ecosystem: pip
patched:
  - chainlit 2.12.0
scores:
  cna: 5.4
  osv: 7.2
ingestedAt: '2026-11-03T19:08:53.338Z'
---

## Overview

Chainlit 2.12.0 contains a server-side request forgery vulnerability that allows unauthenticated attackers to bypass path-scoped MCP allowed_urls entries because validate_mcp_url does not reject the semicolon character. Attackers can submit MCP URLs with '..;' segments to the /mcp endpoint, causing requests to paths outside the operator's grant on origins that strip semicolon path parameters.

## Affected

- `Chainlit 2.12.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-120492)

Affected packages:

- `chainlit >= 2.4.0rc0, < 2.12.0`

Patched in:

- `chainlit 2.12.0`

Source: https://osv.dev/vulnerability/GHSA-hvfh-5mj3-5f3j