CVE-2026-70656

MEDIUMPre-NVD 4.94.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (46th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
4.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 4.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
4.9
EG Score
4.9MEDIUMmedium confidence
EG Risk
27
EG Risk 27/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity49% × 45%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
46th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 21, 2026

Last Modified

September 18, 2026

Advisory Details (5)

Auto-updated Aug 21, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github, github_commit.
githubMentions a patch (unverified)🟡 PoC Available

Regular Expression Denial of Service (ReDoS) via User-Controlled Regex in Monitor Advanced Matching · Advisory · bluewave-labs/Checkmate · GitHub

https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-4c6j-p2cv-wf56
github_release Patch Available

Checkmate v3.9.2

Patch available: bluewave-labs/Checkmate v3.9.2

https://github.com/bluewave-labs/Checkmate/releases/tag/v3.9.2
github_commit

commit d5ec2936ad77 (bluewave-labs/Checkmate)

Fix landed in bluewave-labs/Checkmate commit d5ec2936ad77 — awaiting tagged release

https://github.com/bluewave-labs/Checkmate/commit/d5ec2936ad77ab773529057b442a6eb55dd578eb
github_commit

commit adba25269c45 (bluewave-labs/Checkmate)

Fix landed in bluewave-labs/Checkmate commit adba25269c45 — awaiting tagged release

https://github.com/bluewave-labs/Checkmate/commit/adba25269c455878bf8065bc28cfe5d74e58692f
github_commit

commit 0df71d6356c8 (bluewave-labs/Checkmate)

Fix landed in bluewave-labs/Checkmate commit 0df71d6356c8 — awaiting tagged release

https://github.com/bluewave-labs/Checkmate/commit/0df71d6356c87c747e0b796b0c34e33f2a5203fa

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 49× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-10 20:00 UTCEPSS rescore
  2. 2026-10-09 20:07 UTCEPSS rescore
  3. 2026-10-09 08:02 UTCEG score recompute
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  1. 2026-09-25 04:14 UTCEG score recompute
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  3. 2026-09-23 17:54 UTCEPSS rescore
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  6. 2026-09-21 21:09 UTCEPSS rescore
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  8. 2026-09-20 20:16 UTCEPSS rescore
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  27. 2026-09-08 22:01 UTCEPSS rescore
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  35. 2026-09-04 05:07 UTCEPSS rescore
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  39. 2026-09-01 13:54 UTCEPSS rescore
  40. 2026-09-01 08:41 UTCEG score recompute
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  42. 2026-08-31 07:22 UTCEG score recompute
  43. 2026-08-30 19:17 UTCEPSS rescore
  44. 2026-08-30 06:01 UTCEG score recompute
  45. 2026-08-30 01:22 UTCEPSS rescore
  46. 2026-08-29 04:41 UTCEG score recompute
  47. 2026-08-28 21:42 UTCEPSS rescore
  48. 2026-08-28 03:20 UTCEG score recompute
  49. 2026-08-27 01:56 UTCEG score recompute
  50. 2026-08-26 14:47 UTCEPSS rescore
  51. 2026-08-26 00:37 UTCEG score recompute
  52. 2026-08-25 13:49 UTCEPSS rescore
  53. 2026-08-24 23:19 UTCEG score recompute
  54. 2026-08-23 22:00 UTCEG score recompute
  55. 2026-08-23 00:19 UTCEPSS rescore
  56. 2026-08-21 18:18 UTCEG score recompute
  57. 2026-08-21 18:04 UTCEG score recompute
  58. 2026-08-21 18:04 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-70656?
CVE-2026-70656 is a medium vulnerability published on August 21, 2026. 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…
When was CVE-2026-70656 disclosed?
CVE-2026-70656 was first published on August 21, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-70656 actively exploited?
CVE-2026-70656 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (46th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-70656?
CVE-2026-70656 has a CVSS base score of 4.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-70656?
A fix for CVE-2026-70656 is available: update to the fixed version the vendor names in its advisory.

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