CVE-2024-21636

view_component Cross-site Scripting vulnerability

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

Sanitize the return value of #call, eg:

class MyComponent < ApplicationComponent
  def call
    html_escape("<div>#{user_input}</div>")
  end
end

References

Are there any links users can visit to find out more?

https://github.com/ViewComponent/view_component/pull/1950

For more information

If you have any questions or comments about this advisory:

Open an issue in the github/view_component project.

What kind of vulnerability is it? Who is impacted?

This is an XSS vulnerability that has the potential to impact anyone rendering a component directly from a controller with the view_component gem. Note that only components that define a #call method (i.e. instead of using a sidecar template) are affected. The return value of the #call method is not sanitized and can include user-defined content.

In addition, the return value of the #output_postamble method is not sanitized, which can also lead to XSS issues.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2024-21636 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.9.0, 2.83.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Has the problem been patched? What versions should users upgrade to?

Versions 3.9.0 has been released and fully mitigates both the #call and the #output_postamble vulnerabilities.

1. What is CVE-2024-21636? CVE-2024-21636 is a medium-severity cross-site scripting (XSS) vulnerability in view_component (rubygems), affecting versions >= 3.0.0, < 3.9.0. It is fixed in 3.9.0, 2.83.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2024-21636? CVE-2024-21636 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of view_component are affected by CVE-2024-21636? view_component (rubygems) versions >= 3.0.0, < 3.9.0 is affected.
4. Is there a fix for CVE-2024-21636? Yes. CVE-2024-21636 is fixed in 3.9.0, 2.83.0. Upgrade to this version or later.
5. Is CVE-2024-21636 exploitable, and should I be worried? Whether CVE-2024-21636 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-21636 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-21636?
   • Upgrade view_component to 3.9.0 or later
   • Upgrade view_component to 2.83.0 or later

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