Marko: XSS via case-insensitive script/style closing tag bypass in runtime HTML escaping
Published May 8, 2026
6.4
MEDIUMCVSS 3.1
EPSS 0.27%
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.
Affected products
-
- Version @marko/runtime-tags < 6.0.164StatusaffectedConstraints-
- Version marko < 5.38.36StatusaffectedConstraints-
- Version
- < 5.38.36
- < 6.0.164
No data.
No Red Hat product state for this CVE.
marko
npm
Introduced 0 Fixed 5.38.36@marko/runtime-tags
npm
Introduced 0 Fixed 6.0.164
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| npm | marko | 0 | 5.38.36 |
| npm | @marko/runtime-tags | 0 | 6.0.164 |
Remediation
No remediation recorded yet.
References (4)
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-28790 Advisory
- https://github.com/advisories/GHSA-x9fj-57fh-c8wq Advisory
- https://github.com/marko-js/marko/security/advisories/GHSA-x9fj-57fh-c8wq exploitx_refsource_CONFIRMMitigationPatchVendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-41591
| Link | Providers | Tags |
|---|---|---|
| https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-28790 | Advisory | |
| https://github.com/advisories/GHSA-x9fj-57fh-c8wq | Advisory | |
| https://github.com/marko-js/marko/security/advisories/GHSA-x9fj-57fh-c8wq | exploitx_refsource_CONFIRMMitigationPatchVendor Advisory | |
| https://nvd.nist.gov/vuln/detail/CVE-2026-41591 |
Change history (0)
No recorded changes yet.