dbcve.org
Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-43887

HIGH · 7.3 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 →
77/100
Remediation priority · High
Remotely reachable

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 1.6.1, the Outline comment section permits users to mention other users; however, the backend does not validate or sanitize the href attribute associated with these mentions. As a result, potentially dangerous protocols (e.g., javascript:) are not filtered, introducing a risk of client-side code execution. This vulnerability is fixed in 1.7.0.

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 1.6.1, the comment section's user mention feature fails to validate or sanitize the href attribute, allowing dangerous protocols like javascript: to pass through unfiltered. This enables stored XSS via crafted mentions that execute client-side code when rendered.

MitigationUpgrade to Outline version 1.7.0 or later, which implements proper href attribute validation and filtering.

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/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. Identify if Outline is installed
    Check for Outline running as a service, in Docker containers, or as a hosted application in your environment
    Affected if Outline is present in your environment
  2. Determine the installed Outline version
    Access the Outline admin interface, check package.json, Docker labels, or API /api/status endpoint to find the version number
    Affected if The version falls within 0.84.0 to 1.6.1 inclusive
  3. Verify the comment feature is enabled
    Check Outline settings or documentation configuration to confirm the comments module is active
    Affected if Comments are enabled and accessible to users
  4. Confirm user mention functionality exists
    Check if users can mention other users in comments through the @username syntax
    Affected if The mention feature is available in the comment section

You are affected if Outline versions 0.84.0 through 1.6.1 are installed AND the comment section with user mentions is enabled for users.

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 1.7.0 or later, which implements proper href attribute validation and filtering.

Recommended fix High confidence

Outline version 1.7.0 or later

  1. Check current Outline version by accessing the /api/status endpoint or checking the admin panel
  2. If version is between 0.84.0 and 1.6.1 inclusive, plan upgrade to version 1.7.0 or later
  3. Review Outline upgrade documentation for your deployment method (Docker, npm, etc.)
  4. Create a backup of the Outline database and configuration files
  5. Stop the Outline service before upgrading
  6. Upgrade Outline to version 1.7.0 or latest stable release
  7. Verify the upgrade was successful by checking the version number
  8. Restart the Outline service
Caveat Review the 1.7.0 release notes for any configuration changes or new features that may affect your setup

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

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2026-43887 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data