CVE-2026-44896 PUBLISHED

Mistune: XSS via unescaped figclass/figwidth in Figure directive

Assigner: GitHub_M
Reserved: 07.05.2026 Published: 26.05.2026 Updated: 27.05.2026

Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and realier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS Score: 5.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	Low
Attack Complexity	Low	Integrity	None	Integrity	Low
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	lepture
Product	mistune
Versions	Version <= 3.2.0 is affected

References

https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE