CVE-2026-66420 MeshCentral Cross-Site WebSocket Hijacking via Origin Validation Bypass on Self-Signed Certificate Deployments
Attackers can hijack administrator sessions and gain full control of managed devices by bypassing origin validation on self-signed certificate deployments.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-66420?
CVE-2026-66420 is a high-severity authentication bypass vulnerability in Ylianst MeshCentral, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-346
Which versions are affected by CVE-2026-66420?
How do I fix CVE-2026-66420?
No fix has been published for CVE-2026-66420 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-66420 being exploited?
There is no known exploitation of CVE-2026-66420 in the wild and no public exploit code.
Sources
Also known as GHSA-fcvp-v754-r7rh.