CVE-2026-42889 CRITICAL

CVE-2026-42889: Relay Server WebSocket authentication bypass when token is omitted

Vendor No-Instructions
Product relay-server
Weakness CWE-863 · Incorrect authorization
Published May 12, 2026
Last update May 13, 2026

CVSS base score

9.1/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

May 12, 2026 CVE published
May 13, 2026 Record updated