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

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CRITICAL

Relay Server WebSocket authentication bypass when token is omitted

Published May 12, 2026

9.1

CRITICAL

CVSS 3.1

EPSS 0.53%

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

Vendor No-Instructions Product Relay-Server Default
n/a
- Version
  >= 0.9.0, < 0.9.7
  Status
  affected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

No-Instructions

Relay-Server

n/a

Version	Status	Constraints
>= 0.9.0, < 0.9.7	affected	-

Remediation

No remediation recorded yet.

Weaknesses (2)

CWE-639

Authorization Bypass

CWE-863

Incorrect Authorization

References (2)

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-29792
Advisory
https://github.com/No-Instructions/relay-server/security/advisories/GHSA-9vp9-8q9j-8mqm
exploitx_refsource_CONFIRM

Link	Providers	Tags
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-29792		Advisory
https://github.com/No-Instructions/relay-server/security/advisories/GHSA-9vp9-8q9j-8mqm		exploitx_refsource_CONFIRM