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Possible XSS vulnerability with certain configurations of rails-html-sanitizer

Moderate severity GitHub Reviewed Published Dec 13, 2022 in rails/rails-html-sanitizer • Updated Sep 14, 2023

Package

bundler rails-html-sanitizer (RubyGems)

Affected versions

< 1.4.4

Patched versions

1.4.4

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:

  1. 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

  1. using a :tags option to the Action View helper sanitize:
<%= 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

  1. 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"]
  1. using a :tags options to the Rails::Html::SafeListSanitizer instance method sanitize:
# 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

Credit

This vulnerability was responsibly reported by Dominic Breuker.

References

@flavorjones flavorjones published to rails/rails-html-sanitizer Dec 13, 2022
Published to the GitHub Advisory Database Dec 13, 2022
Reviewed Dec 13, 2022
Published by the National Vulnerability Database Dec 14, 2022
Last updated Sep 14, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS score

0.108%
(45th percentile)

Weaknesses

CVE ID

CVE-2022-23519

GHSA ID

GHSA-9h9g-93gc-623h
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