CVE-2026-67422

The record

pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.

Affected packages

Related vulnerabilities

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• CVE-2026-106454 Twisted is an event-based framework for internet applications, supporting Python 3.6+. CWE-1333
• CVE-2026-77387 geopy is a geocoding library for Python. CWE-1333
• CVE-2026-102990 basic-ftp is an FTP client for Node.js. CWE-1333
• CVE-2026-102473 A flaw was found in dash. CWE-1333
• CVE-2026-102270 PyJWT is a Python implementation of JSON Web Token standards. CWE-1333
• CVE-2026-101906 Axios is a promise-based HTTP client for the browser and Node.js. CWE-1333
• CVE-2026-101903 Axios is a promise-based HTTP client for the browser and Node.js. CWE-1333