CVE-2026-70656 Checkmate: Regular Expression Denial of Service (ReDoS) via User-Controlled Regex in Monitor Advanced Matching
An authenticated admin can cause a denial of service by submitting a malicious regex in monitor settings, freezing the application for all users.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-70656?
CVE-2026-70656 is a medium-severity denial of service vulnerability in bluewave-labs Checkmate, published on 21 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official 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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-70656?
How do I fix CVE-2026-70656?
No fix has been published for CVE-2026-70656 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-70656 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-70656 exists.
Sources
Also known as GHSA-4c6j-p2cv-wf56.