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VulnerabilityPublished

CVE-2026-41591: marko · Cross-site Scripting

Affects markoSource CVE Database V5

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Not known to be exploited · CVSS 6.4 Medium : upgrade to 5.38.36 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
6.4Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 5.38.36
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade marko to 5.38.36.

Affected software

ProductAffectedFixed in
marko-jsmarkoAffected
  • =marko < 5.38.36
  • =@marko/runtime-tags < 6.0.164
Fixed in–
npmmarkopkg:npm/markoOther threatsAffected
  • <5.38.36
Fixed in
  • 5.38.36

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability is patched in marko version 5.38.36 and @marko/runtime-tags version 6.0.164. Users of affected versions should upgrade to these or later versions to remediate the issue. Patch status is confirmed by the vendor advisory stating the fix is included in these releases. No additional mitigation steps are indicated.

Description

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.

References

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