---
id: CVE-2026-70656
title: >-
  Checkmate is an open-source, self-hosted tool designed to track and monitor
  server hardware, uptime, response times, and incidents in real-time with
  beautiful visualizations
summary: >-
  Checkmate is an open-source, self-hosted tool designed to track and monitor
  server hardware, uptime, response times, and incidents in real-time with
  beautiful visualizations. From 3.5.1 until 3.9.2, an authenticated admin or
  superadmin c…
severity: medium
cvss: 4.9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-1333
published: '2026-08-21'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T20:09:01.757'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-70656'
references:
  - url: >-
      https://github.com/bluewave-labs/Checkmate/commit/0df71d6356c87c747e0b796b0c34e33f2a5203fa
    label: security-advisories@github.com
  - url: >-
      https://github.com/bluewave-labs/Checkmate/commit/adba25269c455878bf8065bc28cfe5d74e58692f
    label: security-advisories@github.com
  - url: >-
      https://github.com/bluewave-labs/Checkmate/commit/d5ec2936ad77ab773529057b442a6eb55dd578eb
    label: security-advisories@github.com
  - url: 'https://github.com/bluewave-labs/Checkmate/releases/tag/v3.9.2'
    label: security-advisories@github.com
  - url: >-
      https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-4c6j-p2cv-wf56
    label: security-advisories@github.com
  - url: >-
      https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-4c6j-p2cv-wf56
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00505
epssPercentile: 0.42192
ingestedAt: '2026-09-18T20:51:25.655Z'
---

## Overview

Checkmate is an open-source, self-hosted tool designed to track and monitor server hardware, uptime, response times, and incidents in real-time with beautiful visualizations. From 3.5.1 until 3.9.2, an authenticated admin or superadmin can set matchMethod to regex and place a malicious expression in the expectedValue field for advanced HTTP monitor matching. server/src/api/validation/monitorValidation.ts accepts the expression, and server/src/service/network/AdvancedMatcher.ts synchronously evaluates it against an attacker-controlled HTTP response body on the Node.js main event loop without a timeout or worker isolation, allowing catastrophic backtracking to freeze API endpoints, monitor checks, and WebSocket connections for all users. This issue is fixed in version 3.9.2.

## Remediation

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