UBUNTU-CVE-2026-59928
Mistune, a Python Markdown parser, has a denial of service vulnerability prior to version 3.3.0. The issue arises when processing Markdown documents with many repeated or distinct reference-link definitions, causing quadratic CPU workload and potential exhaustion. This vulnerability is fixed in version 3.3.0.
AI Analysis
Technical Summary
Mistune versions prior to 3.3.0 contain a denial of service vulnerability due to inefficient handling of repeated or distinct reference-link definitions in Markdown documents. Specifically, the quadratic computational complexity in src/mistune/block_parser.py and the ref_links environment dictionary can be exploited to exhaust CPU resources. The vulnerability is resolved in Mistune 3.3.0.
Potential Impact
An attacker can cause a denial of service by submitting specially crafted Markdown documents that trigger excessive CPU consumption, leading to service disruption. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this issue is fixed. No other mitigation is indicated. Patch status is confirmed by the vendor advisory stating the fix is in version 3.3.0.
UBUNTU-CVE-2026-59928
Description
Mistune, a Python Markdown parser, has a denial of service vulnerability prior to version 3.3.0. The issue arises when processing Markdown documents with many repeated or distinct reference-link definitions, causing quadratic CPU workload and potential exhaustion. This vulnerability is fixed in version 3.3.0.
CVSS v3.1
Score 7.5high
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
Mistune versions prior to 3.3.0 contain a denial of service vulnerability due to inefficient handling of repeated or distinct reference-link definitions in Markdown documents. Specifically, the quadratic computational complexity in src/mistune/block_parser.py and the ref_links environment dictionary can be exploited to exhaust CPU resources. The vulnerability is resolved in Mistune 3.3.0.
Potential Impact
An attacker can cause a denial of service by submitting specially crafted Markdown documents that trigger excessive CPU consumption, leading to service disruption. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this issue is fixed. No other mitigation is indicated. Patch status is confirmed by the vendor advisory stating the fix is in version 3.3.0.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-59928
- 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: 6a58b44f68715ace43d6b6ed
Added to database: 07/16/2026, 10:37:03 UTC
Last enriched: 07/16/2026, 11:30:02 UTC
Last updated: 07/31/2026, 19:24:47 UTC
Views: 4
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