CVE-2026-41591: Openjsf Marko

Medium severity, CVSS 6.4. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Openjsf Marko: before 5.38.36 (fixed in 5.38.36)
• Openjsf Marko/runtime-Tags: before 6.0.164 (fixed in 6.0.164)

Published 2026-05-08. Last modified 2026-08-26.