Vulnerability Details CVE-2026-44897
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 9.3%
CVSS Severity
CVSS v3 Score 6.1
References
Products affected by CVE-2026-44897
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cpe:2.3:a:mistune_project:mistune:0.1.0
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cpe:2.3:a:mistune_project:mistune:0.2.0
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cpe:2.3:a:mistune_project:mistune:0.3.0
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cpe:2.3:a:mistune_project:mistune:0.3.1
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cpe:2.3:a:mistune_project:mistune:0.4
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cpe:2.3:a:mistune_project:mistune:0.4.1
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cpe:2.3:a:mistune_project:mistune:0.5
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cpe:2.3:a:mistune_project:mistune:0.5.1
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cpe:2.3:a:mistune_project:mistune:0.6
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cpe:2.3:a:mistune_project:mistune:0.7
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cpe:2.3:a:mistune_project:mistune:0.7.1
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cpe:2.3:a:mistune_project:mistune:0.7.2
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cpe:2.3:a:mistune_project:mistune:0.7.3
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cpe:2.3:a:mistune_project:mistune:0.7.4
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cpe:2.3:a:mistune_project:mistune:0.8
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cpe:2.3:a:mistune_project:mistune:0.8.1
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cpe:2.3:a:mistune_project:mistune:0.8.2
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cpe:2.3:a:mistune_project:mistune:0.8.3
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cpe:2.3:a:mistune_project:mistune:0.8.4
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cpe:2.3:a:mistune_project:mistune:2.0.0
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cpe:2.3:a:mistune_project:mistune:2.0.1
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cpe:2.3:a:mistune_project:mistune:2.0.2
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cpe:2.3:a:mistune_project:mistune:2.0.3
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cpe:2.3:a:mistune_project:mistune:2.0.4
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cpe:2.3:a:mistune_project:mistune:2.0.5
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cpe:2.3:a:mistune_project:mistune:3.0.0
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cpe:2.3:a:mistune_project:mistune:3.0.1
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cpe:2.3:a:mistune_project:mistune:3.0.2
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cpe:2.3:a:mistune_project:mistune:3.1.0
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cpe:2.3:a:mistune_project:mistune:3.1.1
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cpe:2.3:a:mistune_project:mistune:3.1.2
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cpe:2.3:a:mistune_project:mistune:3.1.3
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cpe:2.3:a:mistune_project:mistune:3.1.4
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cpe:2.3:a:mistune_project:mistune:3.2.0