CVE-2026-44899

4.7 MEDIUM
Published: May 26, 2026 Modified: May 28, 2026
View on NVD

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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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/lepture/mistune/releases/tag/v3.2.1
Source: security-advisories@github.com
Product Release Notes
https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9
Source: security-advisories@github.com
Exploit Vendor Advisory
https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Exploit Vendor Advisory

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
4.7 / 10.0
EPSS (Exploit Probability)
0.2%
9th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

mistune_project