CVE-2026-44899
Mistune Image Directive CSS Injection Vulnerability
CVSS Score
4.7
EPSS Score
0.0%
EPSS Percentile
9th
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.
| CWE | CWE-79 |
| Vendor | lepture |
| Product | mistune |
| Published | May 26, 2026 |
| Last Updated | May 27, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
None
Availability
None
Affected Versions
lepture / mistune
< 3.2.1