Bug 2481735 (CVE-2026-44897)

Summary: CVE-2026-44897 mistune: Mistune: Cross-site scripting (XSS) via improper sanitization of HTML heading ID attribute
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anthomas, ehelms, ggainey, jkoehler, jpasqual, juwatts, lphiri, mhulan, nmoumoul, osousa, pcreech, rchan, rjohnson, smallamp, tmalecek
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in Mistune, a Python Markdown parser. A remote attacker could exploit this vulnerability by providing specially crafted input to the HTMLRenderer.heading() function. This input, containing a double-quote character in the HTML heading's ID attribute, is not properly sanitized, allowing the attacker to inject arbitrary attributes. This can lead to cross-site scripting (XSS), potentially resulting in information disclosure or integrity compromise.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-05-26 22:02:38 UTC 
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.