How severe is CVE-2024-53986?

No CVSS score has been assigned to CVE-2024-53986 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2024-53986?

CVE-2024-53986 affects the following packages: rails-html-sanitizer (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2024-53986?

Update rails-html-sanitizer to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-53986 is resolved across your whole dependency graph.

How do I detect CVE-2024-53986 in my RubyGems dependencies?

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.

How do I mitigate CVE-2024-53986 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2024-53986 actively exploited in the wild?

No public exploit code has been indexed for CVE-2024-53986 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2024-53986?

CVE-2024-53986 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 41th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2024-53986?

CVE-2024-53986 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2024-53986 published, and has it been updated?

CVE-2024-53986 was published on December 2, 2024 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎 RubyGems

Not in CISA KEV

CVE-2024-53986 — rails-html-sanitizer

Fix: rails/rails-html-sanitizer@f02ffbb

CVE-2024-53986 is a Cross-site Scripting (XSS) vulnerability in rails-html-sanitizer. 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 1.6.0

Also known asGHSA-638j-pmjw-jq48

Published

Dec 2, 2024

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2024-53986.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

💎rails-html-sanitizer

Real-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 :tags option to the Action View helper sanitize:

<%= 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 :tags options to the Rails::HTML5::SafeListSanitizer instance method sanitize:

# 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_vendor and config.action_text.sanitizer_vendor for more information).

References

Credit

This vulnerability was responsibly reported by So Sakaguchi (mokusou) and taise.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`rails-html-sanitizer`	≥ 1.6.0&&< 1.6.1	1.6.1`bundle update rails-html-sanitizer --conservative`

Affected Products

1 product · 1 configurations

Application

rails html sanitizersrubyonrails

1 version

1.6.0

Detection & mitigation playbook

Open-source dependency

Detect
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 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-53986 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

## 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 HTM

O3 Security · Impact-Aware SCA

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