GHSA-638j-pmjw-jq48
GHSA-638j-pmjw-jq48 is a Cross-site Scripting (XSS) vulnerability in rails-html-sanitizer. O3 Security confirms whether GHSA-638j-pmjw-jq48 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
rails-html-sanitizer has XSS vulnerability with certain configurations
Blast Radius
rails-html-sanitizerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
There is a possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer 1.6.0 when used with Rails >= 7.1.0.
- Versions affected: 1.6.0
- Not affected: < 1.6.0
- Fixed versions: 1.6.1
Impact
A possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer may allow an attacker to inject content if HTML5 sanitization is enabled and the application developer has overridden the sanitizer's allowed tags in the following way:
- the "math" and "style" elements are both explicitly allowed
Code is only impacted if Rails is configured to use HTML5 sanitization, please see documentation for config.action_view.sanitizer_vendor and config.action_text.sanitizer_vendor for more information on these configuration options.
The default configuration is to disallow these elements. Code is only impacted if allowed tags are being overridden. Applications may be doing this in a few different ways:
- using application configuration to configure Action View sanitizers' allowed tags:
# In config/application.rb
config.action_view.sanitized_allowed_tags = ["math", "style"]
see https://guides.rubyonrails.org/configuring.html#configuring-action-view
- using a
:tagsoption to the Action View helpersanitize:
<%= sanitize @comment.body, tags: ["math", "style"] %>
see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize
- setting Rails::HTML5::SafeListSanitizer class attribute
allowed_tags:
# class-level option
Rails::HTML5::SafeListSanitizer.allowed_tags = ["math", "style"]
(note that this class may also be referenced as Rails::Html::SafeListSanitizer)
- using a
:tagsoptions to the Rails::HTML5::SafeListSanitizer instance methodsanitize:
# instance-level option
Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "style"])
(note that this class may also be referenced as Rails::Html::SafeListSanitizer)
- setting ActionText::ContentHelper module attribute
allowed_tags:
ActionText::ContentHelper.allowed_tags = ["math", "style"]
All users overriding the allowed tags by any of the above mechanisms to include both "math" and "style" should either upgrade or use one of the workarounds.
Workarounds
Any one of the following actions will work around this issue:
- Remove "math" or "style" from the overridden allowed tags,
- Or, downgrade sanitization to HTML4 (see documentation for
config.action_view.sanitizer_vendorandconfig.action_text.sanitizer_vendorfor more information).
References
- CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9)
- Original report: https://hackerone.com/reports/2519941
Credit
This vulnerability was responsibly reported by So Sakaguchi (mokusou) and taise.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rails-html-sanitizer | ≥ 1.6.0&&< 1.6.1 | 1.6.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rails-html-sanitizer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update rails-html-sanitizer to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-638j-pmjw-jq48 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-638j-pmjw-jq48 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-638j-pmjw-jq48. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-638j-pmjw-jq48 in your dependencies?
O3 detects GHSA-638j-pmjw-jq48 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.