Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mistune Project | Mistune | < 3.2.1 |
Related Weaknesses (CWE)
References
- https://github.com/lepture/mistune/releases/tag/v3.2.1ProductRelease Notes
- https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9ExploitVendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9ExploitVendor Advisory
FAQ
What is CVE-2026-44899?
CVE-2026-44899 is a vulnerability with a CVSS score of 4.7 (MEDIUM). 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"^\...
How severe is CVE-2026-44899?
CVE-2026-44899 has been rated MEDIUM with a CVSS base score of 4.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-44899?
Check the references section above for vendor advisories and patch information. Affected products include: Mistune Project Mistune.