Vulnerability Description
Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an <object> element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase "javascript:", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive. This is not unconditional cross-site scripting. A javascript: URL does not execute through <object data> in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-66843.html
- https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e0
- https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-xmm9-jc22-rc
- https://osv.dev/vulnerability/EEF-CVE-2026-66843
FAQ
What is CVE-2026-66843?
CVE-2026-66843 is a documented vulnerability. Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted pag...
How severe is CVE-2026-66843?
CVSS scoring is not yet available for CVE-2026-66843. Check NVD for updates.
Is there a patch for CVE-2026-66843?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.