Relay Server WebSocket authentication bypass when token is omitted

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.

Problem type

Affected products

No-Instructions

relay-server

>= 0.9.0, < 0.9.7 - AFFECTED

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

x_refsource_CONFIRM

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-42889

Click to expand

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    "dateUpdated": "2026-05-12T19:30:05.552Z",
    "dateReserved": "2026-04-30T18:49:06.712Z",
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          "value": "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."
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              "description": "CWE-863: Incorrect Authorization",
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              "description": "CWE-639: Authorization Bypass Through User-Controlled Key",
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            "scope": "UNCHANGED",
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