UBUNTU-CVE-2026-59930
Mistune, a Python Markdown parser, has a vulnerability in versions prior to 3.3.0 where the toc plugin and TableOfContents directive generate predictable heading IDs as toc_N without slugifying the heading text. This allows attacker-controlled id="toc_N" content to collide with generated anchors, potentially redirecting same-page navigation, CSS selectors, or JavaScript handlers. The issue is fixed in version 3.3.0.
AI Analysis
Technical Summary
The Mistune Markdown parser's toc plugin and TableOfContents directive generate heading IDs in a predictable manner (toc_N) without slugifying the heading text in versions before 3.3.0. This predictable ID generation can be exploited by an attacker who controls id="toc_N" content to cause collisions with generated anchors. Such collisions may redirect same-page navigation, CSS selectors, or JavaScript handlers, potentially impacting the integrity of page navigation and styling. The vulnerability is addressed and fixed in Mistune version 3.3.0.
Potential Impact
The vulnerability allows an attacker to create id="toc_N" elements that collide with the toc plugin's generated anchors, which can redirect or interfere with same-page navigation, CSS selectors, or JavaScript handlers. This results in limited integrity impact but does not affect confidentiality or availability. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this issue is fixed. No other mitigation is indicated or required.
UBUNTU-CVE-2026-59930
Description
Mistune, a Python Markdown parser, has a vulnerability in versions prior to 3.3.0 where the toc plugin and TableOfContents directive generate predictable heading IDs as toc_N without slugifying the heading text. This allows attacker-controlled id="toc_N" content to collide with generated anchors, potentially redirecting same-page navigation, CSS selectors, or JavaScript handlers. The issue is fixed in version 3.3.0.
CVSS v3.1
Score 4.3medium
Affected software
pkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]+really0.8.4-1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Mistune Markdown parser's toc plugin and TableOfContents directive generate heading IDs in a predictable manner (toc_N) without slugifying the heading text in versions before 3.3.0. This predictable ID generation can be exploited by an attacker who controls id="toc_N" content to cause collisions with generated anchors. Such collisions may redirect same-page navigation, CSS selectors, or JavaScript handlers, potentially impacting the integrity of page navigation and styling. The vulnerability is addressed and fixed in Mistune version 3.3.0.
Potential Impact
The vulnerability allows an attacker to create id="toc_N" elements that collide with the toc plugin's generated anchors, which can redirect or interfere with same-page navigation, CSS selectors, or JavaScript handlers. This results in limited integrity impact but does not affect confidentiality or availability. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this issue is fixed. No other mitigation is indicated or required.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-59930
- Osv Schema Version
- 1.7.0
- Aliases
- []
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:26.04:LTS"]
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a58b44f68715ace43d6b6e3
Added to database: 07/16/2026, 10:37:03 UTC
Last enriched: 07/16/2026, 11:29:47 UTC
Last updated: 07/31/2026, 19:24:47 UTC
Views: 4
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