CVE catalog
CVE-2026-44897
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
- Severity
- Medium · CVSS 6.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.23% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | mistune | sid | 3.4.0-1 | fixed |
| Debian | mistune | forky | 3.1.4-1 | vulnerable |
| Debian | mistune | trixie | 3.1.3-1 | vulnerable |
| Debian | mistune | bookworm | 2.0.4-1 | vulnerable |
| Cpe | mistune | Not reported | Not reported | vulnerable |
| Cpe | mistune | Not reported | 3.2.1 | fixed |
| PyPI | mistune | Not reported | 3.2.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | mistune | source | sid | 3.3.4-1 | not yet assigned | Not reported | [1138260] |
| Debian | mistune | source | forky | (unfixed) | not yet assigned | Not reported | [1138260] |
| Debian | mistune | source | trixie | (unfixed) | not yet assigned | Not reported | [1138260] |
| Debian | mistune | source | bookworm | (unfixed) | not yet assigned | Not reported | [1138260] |
| Cpe | mistune | cpe | Not reported | 3.2.1 | Not reported | Not reported | Not reported |
| PyPI | mistune | PyPI | Not reported | 3.2.1 | Not reported | GHSA-V87V-83H2-53W7 | Not reported |
Notes
[trixie] mistune: Minor issue [bookworm] mistune: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-mistune]Affected
Source package: [mistune]
Details (2)
2.0.4-1· all · bookwormAffected
nvd · mistune · debian · bookworm; nvd · mistune · debian · 12
2.0.4-1· all · bookwormAffected
nvd · mistune · debian · bookworm; nvd · mistune · debian · 12
[Debian 13 (Trixie)]
- [python3-mistune]Affected
Source package: [mistune]
Details (2)
3.1.3-1· all · trixieAffected
nvd · mistune · debian · 13
3.1.3-1· all · trixieAffected
nvd · mistune · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_10761-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-44897]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-44897]
- [https://osv.dev/vulnerability/GHSA-v87v-83h2-53w7]
- [https://security-tracker.debian.org/tracker/CVE-2026-44897]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44897.json]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]