CVE-2026-44899
This vulnerability is fixed in 3.2.1.
Does this matter?
Lower severity and a low EPSS score (0.23%). Track it; it rarely justifies an emergency change on its own.
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 3.1
- 6.1 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 0.23% probability · 14th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Affected
- mistune project/mistune
- Source
- security-advisories@github.com
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.