CVE-2026-66370
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.
- Affected products
- Html Sanitize Ex
- Rrrene Htmlsanitizeex
- < 1.5.3
- CVSS 3.1
- 6.1 MEDIUM
- EPSS
- 0.2% (14th percentile)
- Weakness
- CWE-601
- NVD status
- Analyzed
- Published
- 2026-08-06
- Attack patterns
- CAPEC-154
Workaround
Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow input, or define a custom scrubber that omits it. Omitting the id attribute from the page's own forms, or giving them values an attacker cannot predict, removes the anchor the injected form attribute needs.
No indexed exploits for CVE-2026-66370 yet
Our index is partial: it proves presence, never absence
No exploit for CVE-2026-66370 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.