CVE-2026-41591: Marko is a declarative, HTML-based language for building web apps

Routine

MEDIUM 6.4UPGRADEUPGRADE

CVE-2026-41591 is a medium-severity flaw (CVSS 6.4) affecting marko, marko\/runtime-tags. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 HT

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-05-08
Last modified	2026-08-26

Publisher (CNA): GitHub, Inc. · Vendor: openjsf

Last updated 2026-08-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 16:16 UTCPublished CVE record published
2026-08-26 19:16 UTCUpdated Record last modified

openjsf marko UPGRADE

Affected: < 5.38.36

Fixed in: 5.38.36

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls marko

2. UPGRADE to 5.38.36

npm install marko@">=5.38.36"

openjsf marko\/runtime-tags UPGRADE

Affected: < 6.0.164

Fixed in: 6.0.164

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls markoruntime-tags

2. UPGRADE to 6.0.164

npm install markoruntime-tags@">=6.0.164"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-41591?

marko: upgrade to 5.38.36; marko\/runtime-tags: upgrade to 6.0.164. Exact commands for each OS are on this page.

Is CVE-2026-41591 being exploited?

CVE-2026-41591 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-41591 affect?

CVE-2026-41591 affects marko, marko\/runtime-tags. Severity is medium (CVSS 6.4). 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

How urgent is CVE-2026-41591?

Priority 31/100. Public exploit reference

References

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