CVE-2026-44897
Fixed in a distro release EPSS <1%CVSS 6.1
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.
Products: lepture mistune
Fixed upstream
| Ecosystem | Package | Fixed in |
|---|---|---|
| PyPI | mistune | 3.2.1 |
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Chainguard | datahub-ingestion-fips | 1.5.0.1-r2 |
| Chainguard | kubeflow-pipelines-visualization-server | 2.16.1-r2 |
| Debian 12 | mistune | no fix |
| Debian 13 | mistune | no fix |
| Debian 14 | mistune | no fix |
| Ubuntu 16.04 LTS | mistune | no fix |
| Ubuntu 18.04 LTS | mistune | no fix |
| Ubuntu 20.04 LTS | mistune | no fix |
| Ubuntu 22.04 LTS | mistune | no fix |
| Ubuntu 22.04 LTS | mistune0 | no fix |
| Ubuntu 24.04 LTS | mistune | no fix |
| Ubuntu 24.04 LTS | mistune0 | no fix |
| Ubuntu 25.10 | mistune | no fix |
| Ubuntu 25.10 | mistune0 | no fix |
| Ubuntu 26.04 LTS | mistune | no fix |
| Ubuntu 26.04 LTS | mistune0 | no fix |
| Ubuntu 26.10 | mistune | no fix |
| Ubuntu 26.10 | mistune0 | no fix |
| Wolfi | kubeflow-pipelines-visualization-server | 2.16.1-r2 |
| openSUSE Tumbleweed | python-mistune | 3.2.1-1.1 |