CVE-2026-66420

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

Score 8.8 from GitHub Security Advisory (severity: HIGH) published 2026-07-31. The CNA's CVSS baseline 8.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 3 sources updated this week
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 8.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

MeshCentral 1.1.21 contains a cross-site WebSocket hijacking protection bypass vulnerability that allows unauthenticated remote attackers to hijack authenticated administrator sessions by exploiting an unconditional early return in the CheckWebServerOriginName() function within webserver.js when self-signed certificates are in use. Attackers can open cross-origin WebSocket connections to any of the twelve WebSocket endpoints, send crafted action commands to exfiltrate the server sessionKey used to sign session cookies, forge session tokens as arbitrary users, and gain full remote control of all managed devices governed by the MeshCentral instance.

CVSS v3
8.8
EG Score
8.8HIGHmedium confidence
EG Risk
40
EG Risk 40/100CISA 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
Severity88% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
11th
KEV
Not listed

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

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). 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

July 30, 2026

Last Modified

September 24, 2026

Advisory Details (4)

Auto-updated Jul 30, 2026
Patch available. Sources: github_pr, github_commit.
generic

MeshCentral Cross-Site WebSocket Hijacking via Origin Validation Bypass on Self-Signed Certificate Deployments | Advisories | VulnCheck

https://www.vulncheck.com/advisories/meshcentral-cross-site-websocket-hijacking-via-origin-validation-bypass-on-self-signed-certificate-deployments
generic

GitHub - Ylianst/MeshCentral: A complete web-based remote monitoring and management web site. Once setup you can install agents and perform remote desktop session to devices on the local network or over the Internet. · GitHub

https://github.com/Ylianst/MeshCentral
github_commit Patch Available

commit f04c9f4 (Ylianst/MeshCentral)

Patch available: Ylianst/MeshCentral 1.2.1 (contains commit f04c9f4)

https://github.com/Ylianst/MeshCentral/commit/f04c9f4
github_pr Patch Available

Fix origin validation for self-signed certificate deployments

Patch available: Ylianst/MeshCentral 1.2.1 (PR #7882 merged 2026-06-08)

https://github.com/Ylianst/MeshCentral/pull/7882

Vendor Advisories for CVE-2026-66420(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 74× 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.

Showing the most recent 100 of 230 total refreshes for this CVE.

  1. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:13 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
  4. 2026-10-06 23:52 UTCEG score recompute
  5. 2026-10-06 23:52 UTCGHSA enrichment
  6. 2026-10-06 15:18 UTCEPSS rescore
  7. 2026-10-05 19:58 UTCEG score recompute
  8. 2026-10-05 19:58 UTCGHSA enrichment
  9. 2026-10-05 17:43 UTCEPSS rescore
  10. 2026-10-04 23:55 UTCEG score recompute
  11. 2026-10-04 23:55 UTCGHSA enrichment
  12. 2026-10-04 23:22 UTCEPSS rescore
  13. 2026-10-04 06:35 UTCEG score recompute
  14. 2026-10-04 06:35 UTCGHSA enrichment
  15. 2026-10-03 14:26 UTCEPSS rescore
  16. 2026-10-02 17:56 UTCEPSS rescore
  17. 2026-10-02 16:55 UTCEG score recompute
  18. 2026-10-02 16:55 UTCGHSA enrichment
  19. 2026-10-01 19:50 UTCEPSS rescore
  20. 2026-10-01 14:28 UTCGHSA enrichment
  21. 2026-10-01 02:51 UTCEG score recompute
  22. 2026-10-01 02:51 UTCGHSA enrichment
  23. 2026-09-30 15:03 UTCEPSS rescore
  24. 2026-09-29 06:52 UTCEG score recompute
  25. 2026-09-29 06:52 UTCGHSA enrichment
Show 75 more
  1. 2026-09-28 13:52 UTCEPSS rescore
  2. 2026-09-28 06:31 UTCGHSA enrichment
  3. 2026-09-27 18:58 UTCEG score recompute
  4. 2026-09-27 18:58 UTCGHSA enrichment
  5. 2026-09-26 15:59 UTCEPSS rescore
  6. 2026-09-25 04:55 UTCGHSA enrichment
  7. 2026-09-24 15:00 UTCEG score recompute
  8. 2026-09-24 15:00 UTCGHSA enrichment
  9. 2026-09-24 09:00 UTCGHSA enrichment
  10. 2026-09-23 21:27 UTCEG score recompute
  11. 2026-09-23 21:27 UTCGHSA enrichment
  12. 2026-09-23 17:54 UTCEPSS rescore
  13. 2026-09-23 02:44 UTCEG score recompute
  14. 2026-09-23 02:44 UTCGHSA enrichment
  15. 2026-09-22 15:11 UTCEG score recompute
  16. 2026-09-22 15:11 UTCGHSA enrichment
  17. 2026-09-20 20:16 UTCEPSS rescore
  18. 2026-09-20 11:18 UTCGHSA enrichment
  19. 2026-09-19 23:46 UTCEG score recompute
  20. 2026-09-19 23:45 UTCGHSA enrichment
  21. 2026-09-19 04:11 UTCEG score recompute
  22. 2026-09-19 04:11 UTCGHSA enrichment
  23. 2026-09-18 19:28 UTCEPSS rescore
  24. 2026-09-18 13:32 UTCGHSA enrichment
  25. 2026-09-18 01:18 UTCEG score recompute
  26. 2026-09-18 01:18 UTCGHSA enrichment
  27. 2026-09-17 01:27 UTCEG score recompute
  28. 2026-09-17 01:27 UTCGHSA enrichment
  29. 2026-09-16 14:08 UTCEPSS rescore
  30. 2026-09-16 05:31 UTCEG score recompute
  31. 2026-09-16 05:31 UTCGHSA enrichment
  32. 2026-09-16 05:15 UTCEPSS rescore
  33. 2026-09-15 03:12 UTCEG score recompute
  34. 2026-09-15 03:12 UTCGHSA enrichment
  35. 2026-09-14 07:14 UTCGHSA enrichment
  36. 2026-09-13 19:42 UTCEG score recompute
  37. 2026-09-13 19:42 UTCGHSA enrichment
  38. 2026-09-13 07:32 UTCGHSA enrichment
  39. 2026-09-12 19:58 UTCEG score recompute
  40. 2026-09-12 19:58 UTCGHSA enrichment
  41. 2026-09-12 08:25 UTCGHSA enrichment
  42. 2026-09-11 20:52 UTCEG score recompute
  43. 2026-09-11 20:52 UTCGHSA enrichment
  44. 2026-09-11 14:53 UTCEPSS rescore
  45. 2026-09-11 09:37 UTCEPSS rescore
  46. 2026-09-11 09:09 UTCGHSA enrichment
  47. 2026-09-10 21:36 UTCGHSA enrichment
  48. 2026-09-10 10:02 UTCEG score recompute
  49. 2026-09-10 10:02 UTCGHSA enrichment
  50. 2026-09-09 21:06 UTCEG score recompute
  51. 2026-09-09 21:06 UTCGHSA enrichment
  52. 2026-09-09 07:09 UTCEG score recompute
  53. 2026-09-09 07:09 UTCGHSA enrichment
  54. 2026-09-08 22:01 UTCEPSS rescore
  55. 2026-09-07 19:44 UTCEG score recompute
  56. 2026-09-07 19:44 UTCGHSA enrichment
  57. 2026-09-07 16:01 UTCEPSS rescore
  58. 2026-09-06 18:15 UTCEG score recompute
  59. 2026-09-06 18:15 UTCGHSA enrichment
  60. 2026-09-06 13:47 UTCEPSS rescore
  61. 2026-09-06 06:37 UTCGHSA enrichment
  62. 2026-09-05 18:48 UTCEG score recompute
  63. 2026-09-05 18:48 UTCGHSA enrichment
  64. 2026-09-05 15:31 UTCEPSS rescore
  65. 2026-09-05 04:50 UTCEG score recompute
  66. 2026-09-05 04:50 UTCGHSA enrichment
  67. 2026-09-04 11:25 UTCEG score recompute
  68. 2026-09-04 11:25 UTCGHSA enrichment
  69. 2026-09-04 05:07 UTCEPSS rescore
  70. 2026-09-03 21:16 UTCEG score recompute
  71. 2026-09-03 21:16 UTCGHSA enrichment
  72. 2026-09-02 14:12 UTCEPSS rescore
  73. 2026-09-01 22:36 UTCEG score recompute
  74. 2026-09-01 22:36 UTCGHSA enrichment
  75. 2026-09-01 13:54 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-66420?
CVE-2026-66420 is a high vulnerability published on July 30, 2026. MeshCentral 1.1.21 contains a cross-site WebSocket hijacking protection bypass vulnerability that allows unauthenticated remote attackers to hijack authenticated administrator sessions by exploiting an unconditional early return in the CheckWebServerOriginName() function within webserver.js when…
When was CVE-2026-66420 disclosed?
CVE-2026-66420 was first published on July 30, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66420 actively exploited?
CVE-2026-66420 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (11th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66420?
CVE-2026-66420 has a CVSS base score of 8.8 (the CNA's own assessment, by vulncheck; NVD's own analysis pending).
How do I remediate CVE-2026-66420?
A fix for CVE-2026-66420 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-66420 are linked in the Vendor Advisories panel on this page.

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