How severe is CVE-2024-21636?

CVE-2024-21636 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2024-21636?

CVE-2024-21636 affects the following packages: view_component (RubyGems), view_component (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2024-21636?

Update view_component to 3.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-21636 is resolved across your whole dependency graph.

How do I detect CVE-2024-21636 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for view_component, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2024-21636 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-2024-21636 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2024-21636, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2024-21636?

CVE-2024-21636 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 43th 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-2024-21636?

CVE-2024-21636 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-2024-21636 published, and has it been updated?

CVE-2024-21636 was published on January 4, 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

MEDIUM severity

CVE-2024-21636 — view_component

MEDIUMFix: ViewComponent/view_component@0d26944

CVE-2024-21636 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in view_component. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for view_component — see the affected versions and patch details below.

view_component Cross-site Scripting vulnerability

Also known asGHSA-wf2x-8w6j-qw37

Published

Jan 4, 2024

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

1 known

Exploitation data as of Nov 10, 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-2024-21636.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

💎view_component💎view_component

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

Impact

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.

Patches

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.

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.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`view_component`	≥ 3.0.0&&< 3.9.0	3.9.0`bundle update view_component --conservative`
💎RubyGems	`view_component`	all versions	2.83.0`bundle update view_component --conservative`

Affected Products

1 product · 2 configurations

Application

view componentviewcomponent

≥ 3.0.0 && < 3.9.0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

view_component is a framework for building reusable, testable, and encap…

github.comNVDJan 2024

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for view_component, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update view_component to 3.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-21636 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

### Impact _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](https://viewcomponent.org/guide/templates.html#call) (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](https://viewcomponent.org/api.html#output_postamble--string)