CVE-2026-44899
Mistune Image Directive CSS Injection Vulnerability
MEDIUM 6.1EPSS 0.3%
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.
- Affected
- lepture · mistune
- CVSS v3.1 NVD
- 6.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS v3.1 GITHUB
- 4.7 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N - EPSS
- 0.27% chance of exploitation in the next 30 days, 18th percentile
- Published
- 2026-05-26
- Updated
- 2026-05-27