AIKIDO-2026-676279
league/commonmark is vulnerable to Denial of Service (DoS)
75
High Risk
This Affects:
league/commonmarkTL;DR
The SmartPunctExtension and AttributesExtension contain quadratic parsing paths in unpaired-quote text merging, block-level attribute sibling scanning, and class-list rebuilding. Crafted Markdown with many apostrophes, adjacent attribute blocks, or repeated .class attributes forces repeated full copies or re-scans of continuously growing structures. Converting a small crafted input consumes disproportionate CPU time and can exhaust available workers while producing little or no output. The fix appends text in place, records already-walked attribute runs, and joins accumulated classes in a single pass.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you convert untrusted Markdown with the SmartPunctExtension or AttributesExtension registered.
Background info
league/commonmark is vulnerable to Denial of Service (DoS) in versions 1.5.0 - 2.9.0.
How to fix this
Upgrade the league/commonmark library to the patch version.
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SOC 2Compliant
ISO 27001CompliantISO 42001Compliant
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