CVE-2026-42889 Relay Server WebSocket authentication bypass when token is omitted
Unauthenticated attackers can read or modify document contents via WebSocket connections if authentication is configured but tokens are omitted.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-42889?
CVE-2026-42889 is a critical authentication bypass vulnerability in No-Instructions relay-server, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Relay adds real-time collaboration to Obsidian. Relay Server versions 0.9.0 through 0.9.6 contain an authentication bypass in the multi-document WebSocket endpoints. When authentication is configured, WebSocket connections without a token query parameter were incorrectly treated as having full server permissions. An unauthenticated network attacker who knows or guesses a document ID could connect to the document sync WebSocket and read or modify document contents without a valid document token. This vulnerability is fixed in 0.9.7.
Which versions are affected by CVE-2026-42889?
How do I fix CVE-2026-42889?
No fix has been published for CVE-2026-42889 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-2026-42889 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42889 exists.
Sources
Also known as GHSA-9vp9-8q9j-8mqm.