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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2026-42889

CRITICAL · 9.1 CVSS v3.1 Published 2026-05-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Relay Server versions 0.9.0-0.9.6 contain an authentication bypass in multi-document WebSocket endpoints. When authentication is configured, WebSocket connections without a token query parameter were incorrectly treated as having full server permissions, allowing unauthenticated attackers who know or guess a document ID to connect to the document sync WebSocket and read or modify document contents.

MitigationUpgrade Relay Server to version 0.9.7 or later to patch the authentication bypass. Verify that WebSocket authentication is now properly enforced for all connections.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Relay Server version
    Run 'relay-server --version' or check the server binary/package metadata. If running as a service, check the service version or the version reported by the API endpoint (e.g., GET /api/status).
    Affected if The installed version is 0.9.0, 0.9.1, 0.9.2, 0.9.3, 0.9.4, 0.9.5, or 0.9.6.
  2. Verify WebSocket authentication is configured
    Inspect the Relay Server configuration file (commonly relay.conf, config.yaml, or similar) for WebSocket authentication settings. Look for fields such as 'auth', 'websocketAuth', 'tokenAuth', or 'requireAuthentication' set to true or enabled.
    Affected if Authentication is explicitly configured/enabled for WebSocket connections.
  3. Confirm multi-document WebSocket endpoints are in use
    Review the server configuration or API documentation to determine if multi-document sync is enabled. Check for settings like 'multiDocument', 'documentSync', or 'wsMultiDoc' set to true, or identify if the server exposes endpoints such as /ws/sync/{documentId} or /websocket/document.
    Affected if Multi-document WebSocket sync functionality is enabled and accessible.
  4. Inspect WebSocket connection logs for unauthenticated access
    Review server access logs or WebSocket connection logs for entries connecting to document sync endpoints without a 'token' query parameter. Look for patterns like 'GET /ws/sync/... HTTP' or 'WS connect' where the URL does not contain '?token=' or '&token='.
    Affected if There are WebSocket connection logs showing connections to document sync endpoints that lack a token query parameter.

You are affected if running Relay Server versions 0.9.0-0.9.6 with WebSocket authentication enabled and multi-document WebSocket sync in use, and logs show unauthenticated connections to document endpoints.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Relay Server to version 0.9.7 or later to patch the authentication bypass. Verify that WebSocket authentication is now properly enforced for all connections.

Recommended fix High confidence

0.9.7

  1. Upgrade Relay Server from any version 0.9.0-0.9.6 to version 0.9.7 or later
  2. After upgrading, verify that WebSocket endpoints now properly require authentication tokens
  3. Confirm that unauthenticated connections without valid document tokens are rejected

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,570
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42889 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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