Vulnerability Details CVE-2026-44899
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. 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 4.7
References
Products affected by CVE-2026-44899
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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