CVE-2026-59923 Mistune: XSS via percent-encoded javascript URI bypass in safe_url()

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safeurl does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version...

CVE-2026-59923

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safeurl does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version...

CVE-2026-59923

CVE-2026-59923 affects Mistune, a Python Markdown parser. Before 3.3.0, HTMLRenderer.safe_url() does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. The issue is fixed in version 3.3.0. E...

CVE-2026-59923

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safeurl does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version...

CVE-2026-59923 Mistune: XSS via percent-encoded javascript URI bypass in safe_url()

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safeurl does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version...

CVE-2026-59930 Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id="toc_N"` content

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable tocN values without slugifying the heading text, allowing attacker-controlled id="tocN" content to collide with generated anchors and...

CVE-2026-59930

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable tocN values without slugifying the heading text, allowing attacker-controlled id="tocN" content to collide with generated anchors and...

CVE-2026-59930

Mistune (Python Markdown parser) prior to 3.3.0 has a vulnerability in the toc/TableOfContents directive: heading IDs are generated as predictable toc_N values without slugifying the heading text. This can allow attacker-controlled id="toc_N" content to collide with generated anchors, potentially...

CVE-2026-59930

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable tocN values without slugifying the heading text, allowing attacker-controlled id="tocN" content to collide with generated anchors and...

CVE-2026-59930 Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id="toc_N"` content

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable tocN values without slugifying the heading text, allowing attacker-controlled id="tocN" content to collide with generated anchors and...

CVE-2026-59922 Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)

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 ea...

CVE-2026-59922

Mistune (Python Markdown parser) contains a quadratic-time DoS in formatting.py for long runs of marker pairs (x , ==x==, ^^x^^) in the strikethrough/mark/insert plugins. The issue arises from scanning for matching markers from every possible start position, causing CPU exhaustion. It is fixed in...

CVE-2026-59922

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 ea...

CVE-2026-59922 Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)

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 ea...

PT-2026-56511

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.2.1 Description The render admonition function in src/mistune/directives/admonition.py concatenates the :class: option of the Admonition directive into the HTML class attribute without proper escaping. This allows f...

PT-2026-56510

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0 Description A denial of service issue exists in the default parsing process. Long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in...

PT-2026-56509

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0 Description The HTMLRenderer.safe url function fails to block percent-encoded javascript URIs. This allows an attacker to use specially crafted Markdown links or images to bypass URL protections and execute...

PT-2026-56512

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0 Description The safe url filter in src/mistune/renderers/html.py fails to block several legacy or chained URI schemes. While it restricts javascript:, vbscript:, file:, and data:, it allows schemes such as feed:...

PT-2026-56508

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0 Description A flaw in the Python Markdown parser occurs when the strikethrough, mark, or insert plugins scan for matching markers from each possible start position. Specifically, a sequence of closed tilde,...

PT-2026-56519

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.3.0 Description A Python Markdown parser with renderers and plugins contains an issue where a Markdown document with numerous repeated or distinct reference-link definitions triggers quadratic work within...