CVE-2026-59928

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.

PUBLISHED Reserved 2026-07-07 | Published 2026-07-08 | Updated 2026-07-08 | Assigner GitHub_M

Problem types

CWE-407: Inefficient Algorithmic Complexity

CWE-1333: Inefficient Regular Expression Complexity

Product status

References

github.com/...istune/security/advisories/GHSA-ffq3-xpv3-j92q

github.com/...ommit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69

github.com/lepture/mistune/releases/tag/v3.3.0

cve.org (CVE-2026-59928)

nvd.nist.gov (CVE-2026-59928)

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