Vulnerability · Published May 12, 2026 · Assigned by GitHub_M
CVE-2026-42889Relay Server WebSocket authentication bypass when token is omitted
Critical 9.1
In plain English
A critical-severity incorrect authorization in relay-server from No-Instructions. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities).
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| No-Instructions | relay-server | >= 0.9.0, < 0.9.7 |
Weakness: CWE-863, CWE-639 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N