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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2026-43890

HIGH · 7.7 CVSS v3.1 Published 2026-05-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
83/100
Remediation priority · High
Remotely reachable 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
Outline is a service that allows for collaborative documentation. From 0.84.0 to 1.7.0, the subscriptions.create API endpoint in server/routes/api/subscriptions/subscriptions.ts exhibits a broken authorization pattern. When both collectionId and documentId are supplied in the request, the route handler authorizes ONLY the collection branch (line 125 if (collectionId)), while the downstream subscriptionCreator command at server/commands/subscriptionCreator.ts writes the subscription against the documentId (which was never validated). The result is a subscription record pinning the attacker's user to a victim document the attacker has no read access to, on any team in the instance. The schema (server/routes/api/subscriptions/schema.ts) only enforces "at least one of collectionId/documentId" via .refine() — it does NOT enforce mutual exclusivity, so passing both is a valid, schema-conforming request. This vulnerability is fixed in 1.7.1.

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

In Outline versions 0.84.0 to 1.7.0, the subscriptions.create API endpoint has a broken authorization pattern where it only validates collectionId when both collectionId and documentId are provided. The subscriptionCreator command then writes against the unvalidated documentId, allowing attackers to subscribe to victim documents they have no access to across any team in the instance.

MitigationUpgrade to Outline version 1.7.1 or later which contains the fix for this authorization bypass.

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/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. Identify Outline server version
    Check the installed Outline version by querying the API health endpoint, checking the package.json file, or using the command line tool if available (e.g., outline --version or checking docker container tags)
    Affected if Version is 0.84.0 through 1.7.0 inclusive
  2. Verify API authentication is enforced
    Review the Outline server configuration to confirm that API authentication (api.authentication: true) is enabled in the configuration file or environment variables
    Affected if API authentication is disabled or misconfigured, allowing unauthenticated or insufficiently authorized API access
  3. Inspect subscription records for unauthorized access
    Query the database for subscription records where the user_id does not have explicit access to the associated document_id (check the subscriptions table joined with documents or document_shares)
    Affected if Subscription records exist where the subscriber lacks proper document access permissions
  4. Review API access logs for subscriptions.create endpoint
    Examine API request logs for calls to the subscriptions.create endpoint that reference documentIds outside the caller's authorized collections
    Affected if API logs show subscription.create requests with documentIds the requester should not have access to

You are affected if your Outline version is between 0.84.0 and 1.7.0 and the subscriptions.create endpoint is accessible to users who should not have access to certain documents.

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 to Outline version 1.7.1 or later which contains the fix for this authorization bypass.

Recommended fix High confidence

1.7.1

  1. Upgrade Outline from any version between 0.84.0 and 1.7.0 to version 1.7.1 or later
  2. After upgrading, verify the subscriptions.create endpoint now correctly rejects requests where both collectionId and documentId are provided, or properly validates both fields
  3. Confirm that users can no longer subscribe to documents they do not have access to via the API

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
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2026-43890 in production — separate from our analysis above.

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