What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-12 · updated 2026-10-26
• Weakness: CWE-639

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

• No-Instructions relay-server: from 0.9.0, < 0.9.7

References

• https://github.com/No-Instructions/relay-server/security/advisories/GHSA-9vp9-8q9j-8mqm
• https://github.com/No-Instructions/relay-server/security/advisories/GHSA-9vp9-8q9j-8mqm

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