Medium severity4.7GHSA Advisory· Published May 26, 2026· Updated May 28, 2026
CVE-2026-44899
CVE-2026-44899
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mistunePyPI | >= 3.2.0, < 3.2.1 | 3.2.1 |
Affected products
1Patches
Vulnerability mechanics
References
4- github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9nvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-ccfx-mfmx-2fx9ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-44899ghsaADVISORY
- github.com/lepture/mistune/releases/tag/v3.2.1nvdProductRelease NotesWEB
News mentions
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