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CVE-2026-59928 Mistune is a Python Markdown parser with renderers and plugins

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

Affected products and versions

Product Affected versions Fixed in
mistune 3.3 earliest → < 3.3.0 3.3.0

References

Timeline

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