Mistune: XSS via unescaped figclass/figwidth in Figure directive

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-44896
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-26 21:16:39 UTC
Updated2026-05-28 13:43:22 UTC
DescriptionMistune 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.

Risk And Classification

Primary CVSS: v4.0 5.3 MEDIUM from [email protected]

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.000300000 probability, percentile 0.090880000 (date 2026-05-29)

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

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary5.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/C...
4.0CNADECLARED5.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
3.1[email protected]Primary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Mistune Project Mistune All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Lepture Mistune affected <= 3.2.0 Not specified

References

ReferenceSourceLinkTags
github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v [email protected] github.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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