CVE-2026-111759
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Denial of Service in markdown-it via Quadratic Processing Time

Vulnerability report for CVE-2026-111759, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-10-19

Last updated on: 2026-10-19

Assigner: GitHub, Inc.

Description

markdown-it is a Markdown parser. Prior to 14.3.2 and 15.0.2, when typographer: true is enabled, specially crafted Markdown can cause quadratic processing time in the smartquotes rule, potentially leading to denial of service in applications processing untrusted input. Many opening double quotes followed by unmatched closing single quotes cause repeated scans of the entire opener stack. The same issue occurs with the quote types reversed. The default configuration (typographer: false) is not affected, but this option is enabled with high probability. This issue is fixed in versions 14.3.2 and 15.0.2.

CVSS Scores

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Meta Information

Published
2026-10-19
Last Modified
2026-10-19
Generated
2026-10-20
AI Q&A
2026-10-19
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
markdown-it markdown-it >= 15.0.0, < 15.0.2
markdown-it markdown-it < 14.3.2

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.
CWE-407 An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

Attack-Flow Graph

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Executive Summary

This vulnerability in the markdown-it library occurs when the typographer option is enabled. Specially crafted Markdown with many opening double quotes followed by unmatched closing single quotes causes the smartquotes rule to process input in quadratic time, leading to excessive CPU usage and potential denial of service.

Detection Guidance

Check if your markdown-it library version is below 14.3.2 or 15.0.2. Run: npm list markdown-it or grep "markdown-it" package.json. If typographer is enabled, test with crafted input containing mismatched quotes to observe processing delays.

Impact Analysis

If exploited, this vulnerability can cause applications processing untrusted Markdown to become unresponsive or crash due to high CPU consumption. It primarily affects availability of services using vulnerable versions of markdown-it.

Compliance Impact

This vulnerability primarily impacts system availability due to denial-of-service risks from crafted input. GDPR and HIPAA focus on data availability, integrity, and confidentiality; while this CVE does not directly expose data, prolonged DoS could disrupt access to personal or health data, potentially violating availability requirements under these regulations.

Mitigation Strategies

Upgrade markdown-it to version 14.3.2 or 15.0.2. Alternatively, disable the typographer option or the smartquotes rule in your configuration to prevent the issue.

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