UBUNTU-CVE-2026-59927
Mistune, a Python Markdown parser, has a vulnerability in its Include directive prior to version 3.3.0. The directive detects only direct self-includes but not indirect cycles, allowing two markdown files that include each other to cause unbounded recursion. This results in a RecursionError and crashes the rendering process. The issue is fixed in version 3.3.0.
AI Analysis
Technical Summary
The vulnerability in Mistune's Include directive (prior to 3.3.0) arises because it only detects direct self-includes and fails to detect indirect cyclic includes between markdown files. This flaw allows an attacker to craft two markdown files that include each other, triggering unbounded recursion during rendering. The recursion eventually causes a RecursionError, crashing the rendering request. This denial-of-service condition affects the availability of the service using Mistune for markdown rendering. The issue is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial-of-service by triggering unbounded recursion through indirect cyclic includes in markdown files. This leads to a RecursionError and crashes the rendering process, impacting availability. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later where this issue is fixed. No other mitigation is indicated.
UBUNTU-CVE-2026-59927
Description
Mistune, a Python Markdown parser, has a vulnerability in its Include directive prior to version 3.3.0. The directive detects only direct self-includes but not indirect cycles, allowing two markdown files that include each other to cause unbounded recursion. This results in a RecursionError and crashes the rendering process. The issue is fixed in version 3.3.0.
CVSS v3.1
Score 5.3medium
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 vulnerability in Mistune's Include directive (prior to 3.3.0) arises because it only detects direct self-includes and fails to detect indirect cyclic includes between markdown files. This flaw allows an attacker to craft two markdown files that include each other, triggering unbounded recursion during rendering. The recursion eventually causes a RecursionError, crashing the rendering request. This denial-of-service condition affects the availability of the service using Mistune for markdown rendering. The issue is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial-of-service by triggering unbounded recursion through indirect cyclic includes in markdown files. This leads to a RecursionError and crashes the rendering process, impacting availability. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later where this issue is fixed. No other mitigation is indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-59927
- 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: 6a58b44f68715ace43d6b6f2
Added to database: 07/16/2026, 10:37:03 UTC
Last enriched: 07/16/2026, 11:30:12 UTC
Last updated: 07/31/2026, 19:24:49 UTC
Views: 4
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