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Phlex vulnerable to Cross-site Scripting (XSS) via maliciously formed HTML attribute names and values

High severity GitHub Reviewed Published Apr 29, 2024 in phlex-ruby/phlex • Updated May 3, 2024

Package

bundler phlex (RubyGems)

Affected versions

< 1.9.3
>= 1.10.0, < 1.10.2

Patched versions

1.9.3
1.10.2

Description

There is a potential cross-site scripting (XSS) vulnerability that can be exploited via maliciously crafted user data.

The reason these issues were not detected before is the escapes were working as designed. However, their design didn't take into account just how recklessly permissive browser are when it comes to executing unsafe JavaScript via HTML attributes.

Impact

If you render an <a> tag with an href attribute set to a user-provided link, that link could potentially execute JavaScript when clicked by another user.

a(href: user_profile) { "Profile" }

If you splat user-provided attributes when rendering any HTML or SVG tag, malicious event attributes could be included in the output, executing JavaScript when the events are triggered by another user.

h1(**JSON.parse(user_attributes))

Patches

Patches are available on RubyGems for all minor versions released in the last year.

If you are on main, it has been patched since da8f943

Workarounds

Configuring a Content Security Policy that does not allow unsafe-inline would effectively prevent this vulnerability from being exploited.

References

In addition to upgrading to a patched version of Phlex, we strongly recommend configuring a Content Security Policy header that does not allow unsafe-inline. Here’s how you can configure a Content Security Policy header in Rails. https://guides.rubyonrails.org/security.html#content-security-policy-header

References

@joeldrapper joeldrapper published to phlex-ruby/phlex Apr 29, 2024
Published by the National Vulnerability Database Apr 30, 2024
Published to the GitHub Advisory Database May 1, 2024
Reviewed May 1, 2024
Last updated May 3, 2024

Severity

High

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
Unchanged
Confidentiality
High
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:U/C:H/I:L/A:N

EPSS score

0.044%
(11th percentile)

Weaknesses

CVE ID

CVE-2024-32970

GHSA ID

GHSA-9p57-h987-4vgx

Source code

Credits

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