CVE-2026-59928: high-severity vulnerability in lepture mistune
Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions
Published
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.7%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
lepture · mistuneRelated CVEs — lepture mistune
In the same product, most dangerous first.
CVE-2026-59925HIGHinline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairsEPSS 0.6%CVE-2026-59922HIGHMistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)EPSS 0.6%CVE-2026-121437HIGHMistune 3.3.0 before 3.3.4 Quadratic-Time DoS via _process_emphasis_delimitersEPSS 0.6%CVE-2026-33079HIGHMistune ReDoS in LINK_TITLE_RE allows denial of service with crafted Markdown titlesEPSS 0.6%CVE-2026-59927MEDIUMMistune directives/include: mutual `.. include::` recursion crashes the renderer with `RecursionError`, denial of service via two attacker-controlled markdown filesEPSS 0.5%CVE-2026-49851HIGHMistune: Potential DoS via quadratic-time parsing in parse_link_textEPSS 0.5%