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Vulnerabilities

Vulnerability · CVE-2026-41591

Marko is a declarative, HTML-based language for building web apps.

Published May 8, 2026 · catalog updated Aug 26, 2026 · Marko is a declarative,

Check if you run it

No confirmed exploitation is on record for CVE-2026-41591. EPSS is 0.27%. Act only if a listed version of Marko is a declarative, is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Marko is a declarative,).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.27%
Remediation
Advisory link
Affected products
cpe openjsf/marko · cpe openjsf/marko/runtime-tags

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 or 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 or block could break out of the tag with , , 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe openjsf/markoversion unspecified
  • cpe openjsf/marko/runtime-tagsversion unspecified

How to fix CVE-2026-41591

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-41591. EPSS is 0.27%. Act only if a listed version of Marko is a declarative, is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.27%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 8, 2026 · NIST NVD

    Detected

    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 or 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 or block could break out of the tag with , , etc. and inject arbitrary HTM

  2. Aug 26, 2026 · NIST NVD

    Updated

    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 or 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 or block could break out of the tag with , , etc. and inject arbitrary HTM

Sources

  • CVE.orgVulnerability recordCVE-2026-41591

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-41591

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-41591

    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 or tag the Marko runtime failed to prevent tag breakout when the closing tag used

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.