id: PYSEC-2026-2209
published: "2026-05-26T21:16:39.953Z"
modified: "2026-07-13T05:49:57.392852Z"
aliases:
- CVE-2026-44899
- GHSA-ccfx-mfmx-2fx9
details: "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."
affected:
- package:
    name: mistune
    ecosystem: PyPI
    purl: pkg:pypi/mistune
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 3.2.1
  versions:
  - 0.1.0
  - 0.2.0
  - 0.3.0
  - 0.3.1
  - "0.4"
  - 0.4.1
  - "0.5"
  - 0.5.1
  - "0.6"
  - "0.7"
  - 0.7.1
  - 0.7.2
  - 0.7.3
  - 0.7.4
  - "0.8"
  - 0.8.1
  - 0.8.2
  - 0.8.3
  - 0.8.4
  - 2.0.0
  - 2.0.0a1
  - 2.0.0a2
  - 2.0.0a3
  - 2.0.0a4
  - 2.0.0a5
  - 2.0.0a6
  - 2.0.0rc1
  - 2.0.1
  - 2.0.2
  - 2.0.3
  - 2.0.4
  - 2.0.5
  - 2.1.0
  - 3.0.0
  - 3.0.0a1
  - 3.0.0a2
  - 3.0.0a3
  - 3.0.0rc1
  - 3.0.0rc2
  - 3.0.0rc3
  - 3.0.0rc4
  - 3.0.0rc5
  - 3.0.1
  - 3.0.2
  - 3.1.0
  - 3.1.1
  - 3.1.2
  - 3.1.3
  - 3.1.4
  - 3.2.0
  ecosystem_specific: {}
references:
- type: ADVISORY
  url: https://github.com/lepture/mistune/releases/tag/v3.2.1
- type: EVIDENCE
  url: https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9
severity:
- type: CVSS_V3
  score: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N