CVE-2026-70656: Bluewave-Labs Checkmate

Medium severity, CVSS 4.9. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Bluewave-Labs Checkmate: from 3.5.1, before 3.9.2 (fixed in 3.9.2)

Published 2026-08-21. Last modified 2026-09-18.