EUVD-2026-64656

justhtml before 3.11.0 contains a cross-site scripting vulnerability where the default sanitizer bypasses event handler removal in selectedcontent projections. Attackers can inject SVG or MathML elements with event handlers that are cloned and reinserted into output without sanitization, enabling...

CVE-2026-74793

justhtml versions before 3.11.0 are affected by a cross-site scripting (XSS) vulnerability in the default sanitizer. The root cause is that event handler removal is bypassed in selectedcontent projections : an attacker can inject SVG or MathML elements carrying event handlers, which are then clon...

CVE-2026-5751

justhtml versions 1.13.0 and earlier are affected by a parser-differential / mutation XSS (mXSS) vulnerability. The issue occurs when a custom SanitizationPolicy preserves foreign namespaces (e.g., drop_foreign_namespaces=False with allowlisted SVG/MathML elements or raw-text containers such as )...

EUVD-2026-64654

justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting mXSS vulnerability when using a custom SanitizationPolicy that preserves foreign namespaces e.g., dropforeignnamespaces=False with allowlisted SVG/MathML elements or raw-text containers such as...

CVE-2026-5388 justhtml before 1.15.0 Multiple Security Issues

justhtml before 1.15.0 contains multiple security issues in URL sanitization helpers cleanurlvalue/cleanurlinjsstring, HTML serialization, Markdown passthrough htmlpassthrough=True, and several custom sanitization-policy edge cases. Depending on configuration, an attacker can bypass sanitization ...

EUVD-2026-64652

justhtml before 1.15.0 contains multiple security issues in URL sanitization helpers cleanurlvalue/cleanurlinjsstring, HTML serialization, Markdown passthrough htmlpassthrough=True, and several custom sanitization-policy edge cases. Depending on configuration, an attacker can bypass sanitization ...

CVE-2026-5388

justhtml (Python HTML sanitizer library) before 1.15.0 contains multiple sanitization bypass vulnerabilities across URL sanitization helpers, HTML serialization, Markdown passthrough, and custom policy edge cases. Attackers can inject active HTML and JavaScript via vectors such as encoded javascr...

CVE-2026-5389

justhtml versions before 1.13.0 are affected by a cross-site scripting (XSS) vulnerability in the to_markdown() function. The root cause is that attacker-controlled content inside sanitized elements can contain backticks that break out of fixed-length code fences. When the resulting Markdown is ...

EUVD-2026-64653

justhtml versions before 1.13.0 contain a cross-site scripting vulnerability in the tomarkdown function when serializing attacker-controlled pre content. Attackers can place backticks inside sanitized pre elements to break out of fixed-length code fences, allowing raw HTML to execute when the...

CVE-2026-4671 justhtml before 1.18.0 Denial of Service via CSS Selector

justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings via query, matches, or selector-based transforms, run selector matching over very large untrusted documents,...

EUVD-2026-64651

justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings via query, matches, or selector-based transforms, run selector matching over very large untrusted documents,...

CVE-2026-4671

justhtml (Python HTML sanitizer library) versions before 1.18.0 contain multiple denial-of-service vulnerabilities in CSS selector handling and linkification . Attacker-controlled selector strings passed to query(), matches(), or selector-based transforms, or linkification over untrusted text, ca...

PT-2026-79769

justhtml before 1.15.0 contains multiple security issues in URL sanitization helpers clean url value/clean url in js string, HTML serialization, Markdown passthrough html passthrough=True, and several custom sanitization-policy edge cases. Depending on configuration, an attacker can bypass...

PT-2026-79776

justhtml versions are preserved, so untrusted input that is safe in to html — including entity-decoded text e.g. script or text from RCDATA/RAWTEXT-parsed elements like , , , and — can be emitted as raw HTML in the Markdown output, enabling a sanitizer bypass and potential cross-site scripting wh...

PT-2026-79778

justhtml through 1.9.1 fixed in 1.10.0 is vulnerable to uncontrolled recursion leading to denial of service. During JustHTML construction, TreeBuilder.finish unconditionally calls populate selectedcontent, which recursively traverses the DOM tree via find elements/ find element without a depth...

PT-2026-79777

Name of the Vulnerable Software and Affected Versions justhtml versions prior to 1.12.0 Description A mutation cross-site scripting mXSS issue exists during the serialization of raw-text elements, such as and . When the sanitize dom function processes a DOM tree using a custom policy that retains...

PT-2026-79775

Name of the Vulnerable Software and Affected Versions justhtml versions prior to 1.16.0 Description Multiple HTML sanitization bypass issues allow active or dangerous content, such as script or style tags, to survive the sanitization process, potentially leading to cross-site scripting. These...

PT-2026-79768

justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings via query, matches, or selector-based transforms, run selector matching over very large untrusted documents,...

GHSA-JF6W-2MVX-633J justhtml: to_markdown() code-span blank-line breakout enables XSS

justhtml: tomarkdown code-span blank-line breakout enables XSS Summary In justhtml 0.9.0 through 1.21.0, tomarkdown renders text and text inside a link as an inline Markdown code span whose only protection is backtick-fence length. A blank line \n\n in that text terminates the inline span in any...

Infinite loop

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Infinite loop in the handling of CSS selectors and linkification processes. An attacker can cause excessive CPU or memory consumption by supplying specially crafted selector...