CVE-2026-5388Critical· 9.8▾ Midnightjusthtml 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 …
▾ Midnight zone — Critical, or high with PoC / in-the-wild
impact 53.9 · likelihood 0.1 · exploitation 0
Need a working PoC? Pro members can cast a request and our team develops one — it lands right here.
Exploit-prediction probability, daily snapshots since Aug 24.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.3%
0.3% → 0.6%
Last analysed / modified upstream
— → 9.8
medium → critical
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 sanitization to inject active HTML and JavaScript — for example via encoded javascript: URLs, backslash-based relative URLs resolved as remote hosts, markup-breaking programmatic element/attribute names or HTML comments, raw </textarea> reintroduction through Markdown passthrough, or preserved <style>/<meta http-equiv=refresh>/<base href> tags in custom policies. Most custom-policy issues do not affect the default sanitize=True configuration; they primarily affect helper APIs, programmatic DOM construction, html_passthrough=True, and custom policies/transform pipelines.
Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Affected packages:
justhtml < 1.15.0Patched in:
justhtml 1.15.0Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
CVE-2026-7808Critical· 9.8justhtml before 1.16.0 contains multiple HTML sanitization bypass issues that can allow active/dangerous content (e.g., script or style) to survive sanitization, potentially leading to cross-site scripting
CVE-2026-6827Medium· 6.1justhtml before 1.17.0 contains multiple security issues in sanitization, serialization, and programmatic DOM handling
CVE-2026-9769High· 7.5justhtml through 1.9.1 (fixed in 1.10.0) is vulnerable to uncontrolled recursion leading to denial of service
CVE-2026-4671High· 7.5justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification
CVE-2026-5751Medium· 6.1justhtml 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., drop_foreign_namespaces=False with al…
CVE-2026-8630MediumJustHTML Affected by Mutation XSS via Literal Text Serialization in Raw Text Elements (style/script)