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Vulnerability record · CVE-2026-66420 · published 30 July 2026

CVE-2026-66420: Origin validation error vulnerability

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.

8.6 CVSS 4.0 High EPSS 0.22% · top 88.6% CWE-346 · Origin validation error Awaiting Analysis
8.6CVSS 4.0 base score
0.22%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
9 Sep 2026Last modified by NVD

Description

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:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/Ylianst/MeshCentral
https://github.com/Ylianst/MeshCentral/commit/f04c9f4
https://github.com/Ylianst/MeshCentral/pull/7882
https://www.vulncheck.com/advisories/meshcentral-cross-site-websocket-hijacking-via-origin-validation-bypass-on-self-sig

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Source: NIST National Vulnerability Database (record CVE-2026-66420), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.