Attack Chain

1. An attacker identifies a target application using ViewComponent and a vulnerable component that overrides the around_render method.
2. The vulnerable around_render method is designed to return or wrap attacker-influenced HTML-unsafe content, such as a user-supplied message or dynamic data from a database.
3. The attacker crafts a malicious input (e.g., <img src=x onerror=alert(1)>) that, when processed by the application, will be included in the content returned by the around_render method.
4. The application renders the component, invoking the around_render method. Due to the vulnerability, the around_render method's output is not passed through the necessary HTML-escaping boundary.
5. If the component is rendered as part of a collection, the raw, unsafe output from multiple components is joined and then incorrectly marked as html_safe by ViewComponent::Collection#render_in.
6. The browser receives the server response containing the raw, unescaped malicious HTML, which it interprets and executes, leading to Cross-Site Scripting (XSS).
7. Successful execution enables various impacts, including session/token theft, authenticated actions as the victim, data exfiltration, or credential phishing within the trusted application origin.

Impact

Successful exploitation of CVE-2026-54498 results in Cross-Site Scripting (XSS) within applications utilizing affected ViewComponent versions. Depending on the application's context and configuration, this can lead to severe consequences. Attackers could steal user session cookies or authentication tokens, perform authenticated actions on behalf of the victim, bypass Cross-Site Request Forgery (CSRF) protections, exfiltrate sensitive page data, or conduct credential phishing and UI redressing attacks from within the legitimate application domain. The risk is particularly elevated for applications that render components through ViewComponent::Collection, as this path actively marks raw malicious HTML as html_safe, preventing any subsequent security controls from sanitizing the output.

Recommendation

• Patch CVE-2026-54498 immediately by upgrading rubygems/view_component to version 4.12.0 or later.
• Review codebases for vulnerable patterns where around_render returns or wraps user-controlled, HTML-unsafe content. Specifically inspect components that use around_render for tracing, layout wrapping, feature-flag fallbacks, or instrumentation.
• Implement strict input sanitization and output encoding at the application layer for all user-controlled data, especially when displayed in HTML contexts, even after patching.