CVE-2026-44897
Mistune Heading ID Attribute Injection XSS
CVSS Score
6.1
EPSS Score
0.0%
EPSS Percentile
9th
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.
| CWE | CWE-79 |
| Vendor | lepture |
| Product | mistune |
| Published | May 26, 2026 |
| Last Updated | Jun 1, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Affected Versions
lepture / mistune
< 3.2.1