# CVE-2026-70656

## Summary

- **CVE ID:** CVE-2026-70656
- **Severity:** MEDIUM
- **CVSS Score:** 4.9 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-1333
- **Published:** Aug 21, 2026
- **Last Modified:** Aug 21, 2026

## Description

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 (>= 3.5.1, < 3.9.2)

## References

- [CNA](https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-4c6j-p2cv-wf56)
- [CNA](https://github.com/bluewave-labs/Checkmate/commit/0df71d6356c87c747e0b796b0c34e33f2a5203fa)
- [CNA](https://github.com/bluewave-labs/Checkmate/commit/adba25269c455878bf8065bc28cfe5d74e58692f)
- [CNA](https://github.com/bluewave-labs/Checkmate/commit/d5ec2936ad77ab773529057b442a6eb55dd578eb)
- [CNA](https://github.com/bluewave-labs/Checkmate/releases/tag/v3.9.2)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.42%
- **EPSS Percentile:** 35.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._