CVE-2022-23519 — rails-html-sanitizer
HIGHCVE-2022-23519 is a high-severity (CVSS 7.2) Cross-site Scripting (XSS) vulnerability in rails-html-sanitizer. 2 public exploit references exist, so weaponization risk is real. A fix is available for rails-html-sanitizer — see the affected versions and patch details below.
Possible XSS vulnerability with certain configurations of rails-html-sanitizer
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2022-23519 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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.
- Versions affected: ALL
- Not affected: NONE
- Fixed versions: 1.4.4
Impact
A possible XSS vulnerability with certain configurations of Rails::Html::Sanitizer may allow an attacker to inject content if the application developer has overridden the sanitizer's allowed tags in either of the following ways:
- allow both "math" and "style" elements,
- or allow both "svg" and "style" elements
Code is only impacted if allowed tags are being overridden. Applications may be doing this in four different ways:
- using application configuration:
# In config/application.rb
config.action_view.sanitized_allowed_tags = ["math", "style"]
# or
config.action_view.sanitized_allowed_tags = ["svg", "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"] %>
<%# or %>
<%= sanitize @comment.body, tags: ["svg", "style"] %>
see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize
- using Rails::Html::SafeListSanitizer class method
allowed_tags=:
# class-level option
Rails::Html::SafeListSanitizer.allowed_tags = ["math", "style"]
# or
Rails::Html::SafeListSanitizer.allowed_tags = ["svg", "style"]
- using a
:tagsoptions to the Rails::Html::SafeListSanitizer instance methodsanitize:
# instance-level option
Rails::Html::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "style"])
# or
Rails::Html::SafeListSanitizer.new.sanitize(@article.body, tags: ["svg", "style"])
All users overriding the allowed tags by any of the above mechanisms to include (("math" or "svg") and "style") should either upgrade or use one of the workarounds immediately.
Workarounds
Remove "style" from the overridden allowed tags, or remove "math" and "svg" from the overridden allowed tags.
References
- CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9)
- https://hackerone.com/reports/1656627
Credit
This vulnerability was responsibly reported by Dominic Breuker.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rails-html-sanitizer | all versions | 1.4.4bundle update rails-html-sanitizer --conservative |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rails-html-sanitizer to 1.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-23519 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-23519 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-23519. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Satellite 6.13 for RHEL 8 | tfm-rubygem-rails-html-sanitizer-0:1.4.4-1.el8sat | RHSA-2023:2097 |
Frequently Asked Questions
Is CVE-2022-23519 in your dependencies?
O3 Security finds CVE-2022-23519 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.