CVE-2026-59922: high-severity vulnerability in lepture mistune
Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.6%
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, 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-2026-59928HIGHMistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitionsEPSS 0.7%CVE-2026-59925HIGHinline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairsEPSS 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%