CVE-2026-66829 html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection
Attackers can force users to redirect to malicious sites via meta refresh tags in sanitized HTML, requiring an upgrade to the html_sanitize_ex library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-66829?
CVE-2026-66829 is a low-severity vulnerability in rrrene html_sanitize_ex, published on 6 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to force visitors of a page to navigate to a site of the attacker's choosing via a <meta http-equiv="refresh"> element in sanitized HTML. HtmlSanitizeEx.html5/1 keeps attacker-supplied <meta> elements in its output. A meta element acts on the whole document rather than on the fragment it was embedded in, so it can also declare document-wide directives such as Content-Security-Policy.
This is not cross-site scripting. Browsers do not navigate a meta refresh to a javascript: URL, so the uppercase JAVASCRIPT: filter bypass yields no script execution and none was demonstrated.
This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.
Weakness: CWE-601
Which versions are affected by CVE-2026-66829?
1 open source package ship an affected version, including html_sanitize_ex. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
html_sanitize_ex Hex | From 0.3.1 | 1.4.5, 1.5.3 |
Products include Rrrene Htmlsanitizeex.
How do I fix CVE-2026-66829?
Upgrade html_sanitize_ex to a fixed version for your release line: 1.4.5 or 1.5.3.
Is CVE-2026-66829 being exploited?
There is no known exploitation of CVE-2026-66829 in the wild and no public exploit code.
Other vulnerabilities in rrrene html_sanitize_ex
- CVE-2026-68749 Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service
- CVE-2026-68750 Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of service
- CVE-2026-66370 html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allowing form hijacking
- CVE-2026-66843 html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding
- CVE-2026-68747 CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input
Sources
Also known as EEF-CVE-2026-66829, GHSA-2c6f-3j54-xpcr, GHSA-c486-5fvq-fp3v.