Vulnerability Description
URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing. No script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-66370.html
- https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f7
- https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-ww
- https://osv.dev/vulnerability/EEF-CVE-2026-66370
FAQ
What is CVE-2026-66370?
CVE-2026-66370 is a documented vulnerability. URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering...
How severe is CVE-2026-66370?
CVSS scoring is not yet available for CVE-2026-66370. Check NVD for updates.
Is there a patch for CVE-2026-66370?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.