CVE-2026-44899
Last modified
CVE-2026-44899 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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*)?"). EPSS estimates a 0.23% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mistune Project | Mistune | < 3.2.1 |
References
- https://github.com/lepture/mistune/releases/tag/v3.2.1Product, Release Notes
- https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9Exploit, Vendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9Exploit, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
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