CVE-2026-59804 Midscene Bridge Server - Session Hijack via Unauthenticated WebSocket
Unauthenticated attackers can hijack sessions, inject commands, exfiltrate data, or crash the Midscene Bridge Server via cross-origin WebSocket connections.
- 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-2026-59804?
CVE-2026-59804 is a high-severity missing authorization vulnerability in web-infra-dev midscene, published on 8 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
Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.
Which versions are affected by CVE-2026-59804?
How do I fix CVE-2026-59804?
No fix has been published for CVE-2026-59804 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-59804 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59804 exists.
Sources
Also known as GHSA-8rcx-4rjr-4wpf.