CVE-2026-66420

HIGHPre-NVD 8.88.8—
EchelonGraph scoreHIGH 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%CVSS: 8.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
8.8(high)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

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%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
6%
KEV
Not listed

Published

July 30, 2026

Last Modified

August 14, 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 31× in last 7d / 96× 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. 2026-08-21 01:55 UTCEG score recompute
  2. 2026-08-21 01:55 UTCGHSA enrichment
  3. 2026-08-20 22:56 UTCEPSS rescore
  4. 2026-08-20 14:23 UTCGHSA enrichment
  5. 2026-08-20 02:33 UTCEG score recompute
  6. 2026-08-20 02:32 UTCGHSA enrichment
  7. 2026-08-19 17:04 UTCEPSS rescore
  8. 2026-08-19 14:59 UTCGHSA enrichment
  9. 2026-08-19 03:25 UTCGHSA enrichment
  10. 2026-08-18 15:52 UTCEG score recompute
  11. 2026-08-18 15:52 UTCGHSA enrichment
  12. 2026-08-18 13:48 UTCEPSS rescore
  13. 2026-08-18 02:01 UTCGHSA enrichment
  14. 2026-08-17 14:27 UTCEG score recompute
  15. 2026-08-17 14:27 UTCGHSA enrichment
  16. 2026-08-17 13:47 UTCEPSS rescore
  17. 2026-08-17 02:55 UTCGHSA enrichment
  18. 2026-08-16 15:22 UTCEG score recompute
  19. 2026-08-16 15:22 UTCGHSA enrichment
  20. 2026-08-16 14:56 UTCEPSS rescore
  21. 2026-08-16 03:49 UTCEG score recompute
  22. 2026-08-16 03:49 UTCGHSA enrichment
  23. 2026-08-15 16:17 UTCGHSA enrichment
  24. 2026-08-15 04:44 UTCEG score recompute
  25. 2026-08-15 04:44 UTCGHSA enrichment
Show 71 more
  1. 2026-08-15 01:30 UTCEPSS rescore
  2. 2026-08-14 17:11 UTCEG score recompute
  3. 2026-08-14 17:11 UTCGHSA enrichment
  4. 2026-08-14 15:50 UTCGHSA enrichment
  5. 2026-08-14 04:18 UTCEG score recompute
  6. 2026-08-14 04:18 UTCGHSA enrichment
  7. 2026-08-13 22:00 UTCEPSS rescore
  8. 2026-08-13 16:45 UTCGHSA enrichment
  9. 2026-08-13 05:12 UTCGHSA enrichment
  10. 2026-08-12 17:40 UTCEG score recompute
  11. 2026-08-12 17:40 UTCGHSA enrichment
  12. 2026-08-12 13:51 UTCEPSS rescore
  13. 2026-08-12 06:07 UTCGHSA enrichment
  14. 2026-08-11 18:31 UTCEG score recompute
  15. 2026-08-11 18:31 UTCGHSA enrichment
  16. 2026-08-11 06:58 UTCEG score recompute
  17. 2026-08-11 06:58 UTCGHSA enrichment
  18. 2026-08-11 00:00 UTCEPSS rescore
  19. 2026-08-10 19:26 UTCGHSA enrichment
  20. 2026-08-10 07:54 UTCGHSA enrichment
  21. 2026-08-09 20:21 UTCEG score recompute
  22. 2026-08-09 20:21 UTCGHSA enrichment
  23. 2026-08-09 13:47 UTCEPSS rescore
  24. 2026-08-09 08:49 UTCGHSA enrichment
  25. 2026-08-08 21:17 UTCEG score recompute
  26. 2026-08-08 21:17 UTCGHSA enrichment
  27. 2026-08-08 16:37 UTCEPSS rescore
  28. 2026-08-08 09:44 UTCGHSA enrichment
  29. 2026-08-07 22:11 UTCEG score recompute
  30. 2026-08-07 22:11 UTCGHSA enrichment
  31. 2026-08-07 10:39 UTCGHSA enrichment
  32. 2026-08-06 23:06 UTCEG score recompute
  33. 2026-08-06 23:06 UTCGHSA enrichment
  34. 2026-08-06 13:47 UTCEPSS rescore
  35. 2026-08-06 11:34 UTCGHSA enrichment
  36. 2026-08-05 23:58 UTCEG score recompute
  37. 2026-08-05 23:58 UTCGHSA enrichment
  38. 2026-08-05 19:17 UTCEPSS rescore
  39. 2026-08-05 19:17 UTCEPSS rescore
  40. 2026-08-05 12:25 UTCGHSA enrichment
  41. 2026-08-05 00:26 UTCEG score recompute
  42. 2026-08-05 00:25 UTCGHSA enrichment
  43. 2026-08-04 15:10 UTCEPSS rescore
  44. 2026-08-04 12:50 UTCEG score recompute
  45. 2026-08-04 12:49 UTCGHSA enrichment
  46. 2026-08-04 10:39 UTCEPSS rescore
  47. 2026-08-04 01:17 UTCGHSA enrichment
  48. 2026-08-03 13:44 UTCEG score recompute
  49. 2026-08-03 13:44 UTCGHSA enrichment
  50. 2026-08-03 10:36 UTCEPSS rescore
  51. 2026-08-03 02:08 UTCGHSA enrichment
  52. 2026-08-02 14:36 UTCGHSA enrichment
  53. 2026-08-02 03:03 UTCEG score recompute
  54. 2026-08-02 03:03 UTCGHSA enrichment
  55. 2026-08-02 02:27 UTCEPSS rescore
  56. 2026-08-01 15:30 UTCEG score recompute
  57. 2026-08-01 15:30 UTCGHSA enrichment
  58. 2026-08-01 04:16 UTCEPSS rescore
  59. 2026-08-01 03:57 UTCEG score recompute
  60. 2026-08-01 03:57 UTCGHSA enrichment
  61. 2026-07-31 16:24 UTCEG score recompute
  62. 2026-07-31 16:24 UTCGHSA enrichment
  63. 2026-07-31 12:18 UTCEG score recompute
  64. 2026-07-31 12:18 UTCGHSA enrichment
  65. 2026-07-31 12:00 UTCEG score recompute
  66. 2026-07-31 12:00 UTCGHSA enrichment
  67. 2026-07-31 10:56 UTCEG score recompute
  68. 2026-07-31 10:56 UTCGHSA enrichment
  69. 2026-07-30 23:20 UTCEG score recompute
  70. 2026-07-30 22:21 UTCEG score recompute
  71. 2026-07-30 22:20 UTCMITRE cvelistV5first tracked

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 in the National Vulnerability Database on July 30, 2026, with the most recent update on August 14, 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% probability of exploitation in the next 30 days, which ranks it in the top 93.8% of all scored CVEs.
What is the CVSS score of CVE-2026-66420?
CVE-2026-66420 has a CVSS v4.0 base score of 8.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-66420?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66420, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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