CVE-2026-44899

Severity CVSS v4.0:

Pending analysis

Type:

CWE-79 Cross-Site Scripting (XSS)

Publication date:

26/05/2026

Last modified:

28/05/2026

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.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N CVSS v3.1 Severity and Metrics:

Base Score: 4.70 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): Required
Scope (S): Changed
Confidentiality (C): Low
Integrity (I): None
Availability (A): None