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

CVE-2026-42455

HIGH · 8.8 CVSS v4.0 Published 2026-05-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
97/100
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
Linkwarden is a self-hosted, open-source collaborative bookmark manager to collect, organize and archive webpages. In versions 2.14.0 and prior, the archive upload endpoint (POST /api/v1/archives/[linkId]?format=4) accepts HTML files (text/html) without sanitizing JavaScript content. When the archive is later accessed via GET /api/v1/archives/[linkId]?format=4, the HTML is served with Content-Type: text/html from the Linkwarden origin, without any Content-Security-Policy header. This allows arbitrary JavaScript execution in the context of the authenticated Linkwarden sessio. At time of publication, there are no publicly available patches.

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

This is a stored XSS vulnerability in Linkwarden's archive upload feature. The application accepts HTML file uploads (text/html) without sanitizing embedded JavaScript, and later serves these files back with Content-Type: text/html without a Content-Security-Policy header, enabling arbitrary script execution in the context of authenticated user sessions.

MitigationUntil an official patch is released, disable or restrict HTML file uploads to the archive endpoint and implement server-side HTML sanitization (e.g., using DOMPurify) before storage. Additionally, configure Content-Security-Policy headers to block inline script execution.

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
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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 Linkwarden is deployed
    Check running services, container images, or installed packages for Linkwarden. Look for the application responding on its typical port (typically 3000) or check installed packages via package managers.
    Affected if Linkwarden is present in the environment
  2. Determine installed Linkwarden version
    Check the version via the UI (typically in settings/about page), check package.json in the application directory, or query the API endpoint if available. Compare against any released versions after the CVE publication date.
    Affected if The installed version is any release that includes the archive upload feature and has not been patched for this issue
  3. Verify archive upload feature is accessible
    Log into Linkwarden as an authenticated user and navigate to the archive upload functionality. Check if the POST endpoint for file uploads is reachable (typically /api/v1/archives or similar upload paths).
    Affected if The archive upload feature is enabled and accessible to authenticated users
  4. Confirm uploaded archives are served as text/html
    Upload a test HTML file through the archive feature, then retrieve it via the GET endpoint and examine the Content-Type header in the response. Use curl -I to inspect headers without downloading the full content.
    Affected if The Content-Type header is 'text/html' without a restrictive Content-Security-Policy header present
  5. Check for absence of CSP header on archive retrieval
    Retrieve an uploaded archive file and inspect response headers for Content-Security-Policy. Use: curl -I <archive_url> and look for CSP in the headers.
    Affected if No Content-Security-Policy header is present on the archive file GET endpoint

A user is affected if Linkwarden with the archive upload feature is running and uploaded archives are served as text/html without a Content-Security-Policy header, allowing stored XSS execution.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Until an official patch is released, disable or restrict HTML file uploads to the archive endpoint and implement server-side HTML sanitization (e.g., using DOMPurify) before storage. Additionally, configure Content-Security-Policy headers to block inline script execution.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,980
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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-2026-42455 in production — separate from our analysis above.

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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