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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-41591

MEDIUM · 6.4 CVSS v3.1 Published 2026-05-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
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
Marko is a declarative, HTML-based language for building web apps. Prior to marko version 5.38.36 and prior to @marko/runtime-tags 6.0.164, when dynamic text is interpolated into a <script> or <style> tag the Marko runtime failed to prevent tag breakout when the closing tag used non-lowercase casing. An attacker able to place input inside a <script> or <style> block could break out of the tag with </SCRIPT>, </Style>, etc. and inject arbitrary HTML/JavaScript, resulting in cross-site scripting. This issue has been patched in marko version 5.38.36 and @marko/runtime-tags 6.0.164.

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

Marko's template runtime failed to properly sanitize closing tags in script/style contexts when dynamic text interpolation was used. The runtime only checked for lowercase </script> and </style> closing tags, allowing attackers to escape the tag context using non-lowercase variants like </SCRIPT> or </Style>, enabling XSS attacks.

MitigationUpgrade marko to version 5.38.36 or later, or @marko/runtime-tags to version 6.0.164 or later. Review existing uses of dynamic text interpolation inside script/style blocks for any injected content.

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
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/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 Marko template usage
    Search your codebase for marko dependencies in package.json files or check for @marko/runtime-tags and marko packages in node_modules
    Affected if Either marko or @marko/runtime-tags is listed as a dependency
  2. Determine installed marko version
    Run 'npm list marko' or 'npm list @marko/runtime-tags' to see the installed version number, or inspect the version field in node_modules/<package>/package.json
    Affected if The installed version is below 5.38.36 for marko or below 6.0.164 for @marko/runtime-tags
  3. Check for dynamic text in script blocks
    Search .marko template files for <script> tags containing interpolation syntax like ${...} or <#if> inside script contexts
    Affected if Dynamic interpolation is used inside <script> or <style> tags in your templates
  4. Inspect for user-controlled input in templates
    Review the source of values used in script/style interpolations to determine if any originate from user input, URL parameters, or external APIs
    Affected if Any data from untrusted sources flows into dynamic text inside script/style contexts

You are affected if you use an affected version of marko or @marko/runtime-tags AND have dynamic text interpolation inside script or style tags with data that could be controlled by an attacker.

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 marko to version 5.38.36 or later, or @marko/runtime-tags to version 6.0.164 or later. Review existing uses of dynamic text interpolation inside script/style blocks for any injected content.

Recommended fix High confidence

marko >= 5.38.36 and @marko/runtime-tags >= 6.0.164

  1. Identify the marko and @marko/runtime-tags dependencies in your project (check package.json)
  2. Run 'npm list marko @marko/runtime-tags' to see current installed versions
  3. If using marko: upgrade to version 5.38.36 or later by running 'npm install marko@^5.38.36'
  4. If using @marko/runtime-tags: upgrade to version 6.0.164 or later by running 'npm install @marko/runtime-tags@^6.0.164'
  5. Run 'npm update' to ensure all dependencies resolve to compatible versions
  6. Test your application to verify the upgrade does not break functionality
  7. Rebuild and redeploy your application
Caveat Minor/patch upgrades typically maintain backward compatibility but test thoroughly as with any dependency update

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

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
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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-2026-41591 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
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  • No spam, self-promotion, credentials, or personal data