- Severity: MEDIUM
- CVE: CVE-2026-126079
- Ecosystems: rubygems, rubygems
- Packages: actionview, actionview
### Impact
With the HTML5 sanitizer (`Rails::HTML5::Sanitizer`, the default vendor on CRuby for applications using `load_defaults 7.1` or later), Nokogiri before 1.19.5 serializes “ unescaped inside attribute values. The Action View text helpers `highlight` and `simple_format` sanitize their input and then process the resulting HTML as a string: `highlight` splits it on tag boundaries to insert matches, and `simple_format` splits it into paragraphs on blank lines. An unescaped `>` or a blank line inside an attribute value could cause markup in that value, which the sanitizer left inert, to be emitted as live elements in the helper’s `html_safe` output, possibly leading to XSS. Applications that use the HTML5 sanitizer and pass untrusted text to `highlight`, or to `simple_format` with `html_options`, are affected.
### Details
The fixed releases require rails-html-sanitizer 1.7.2 or later, which requires Loofah 2.25.3 and Nokogiri 1.19.5. With these versions, the HTML5 sanitizer escapes “ in attribute values as `<` and `>`, as the HTML4 sanitizer already does. The parsed DOM is unchanged, but code or tests that compare sanitized HTML as a string may see the new serialization.
### Workarounds
Upgrade Nokogiri to 1.19.5 or later; the escaping is in its HTML5 serializer, so no Rails upgrade is needed. Alternatively, use the HTML4 sanitizer by setting `config.action_view.sanitizer_vendor = Rails::HTML4::Sanitizer`.
### Releases
The fixed releases are available at the nor…
Source: GitHub Security Advisories · 2026-11-12