CVE-2026-88059

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.28, 21.2.20, and 22.1.1, Angular's @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. Exploitation requires provideClientHydration, child provideHttpClient delegation through withRequestsMadeViaParent, parent-level credential injection, and an SSR HTML response shared across users by a CDN, reverse proxy, or application cache. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data. Applications can mitigate by attaching credentials at the child, filtering sensitive endpoints with withHttpTransferCacheOptions, disabling transfer caching for sensitive routes, or marking personalized HTML private or no-store. This issue is fixed in versions 20.3.28, 21.2.20, and 22.1.1.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.28, 21.2.20, and 22.1.1, Angular's @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. Exploitation requires provideClientHydration, child provideHttpClient delegation through withRequestsMadeViaParent, parent-level credential injection, and an SSR HTML response shared across users by a CDN, reverse proxy, or application cache. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data. Applications can mitigate by attaching credentials at the child, filtering sensitive endpoints with withHttpTransferCacheOptions, disabling transfer caching for sensitive routes, or marking personalized HTML private or no-store. This issue is fixed in versions 20.3.28, 21.2.20, and 22.1.1.

A security bypass vulnerability was discovered in @angular/common when Server-Side Rendering (SSR) and hydration are enabled in applications using a hierarchical HttpClient configuration with withRequestsMadeViaParent().

The HttpTransferCache utility optimizes hydration by caching outgoing HTTP requests performed during SSR and transferring the cached state to the client-side application via TransferState (serialized as JSON in <script id="ng-state">). Following the remediation of CVE-2026-50170, HttpTransferCache automatically skips caching requests that contain authentication headers or credentials (Authorization, Cookie, withCredentials, etc.).

However, when a child HttpClient delegates to a parent client via withRequestsMadeViaParent(), the child's TransferCache interceptor evaluates whether the request is eligible for caching before delegating to the parent client's interceptor chain.

If an outgoing request originates as anonymous from the child client, the child TransferCache marks the request as cacheable. When the request reaches a parent interceptor that injects sensitive authentication credentials (such as an Authorization header or API token), the parent TransferCache correctly skips caching the authenticated request. However, when the backend returns the private, authenticated response, the child TransferCache still stores the response in TransferState based on its initial pre-delegation evaluation.

Impact

Successful exploitation allows sensitive, user-specific information belonging to an authenticated user to be leaked to unauthenticated or unauthorized users. This occurs when:

1. During SSR, a child HttpClient initiates an unauthenticated request that is subsequently authenticated by a parent interceptor.
2. The authenticated response body is cached into the SSR-rendered HTML page (TransferState).
3. The rendered HTML page is stored by a shared caching layer (e.g., CDN, edge cache, or reverse proxy) or served across user sessions.
4. Subsequent visitors requesting the same page receive the cached HTML containing the previous user's private data.

Attack Preconditions & Vulnerable Configurations

An application is affected only if all of the following conditions are met:

• SSR and Hydration Enabled: The application uses Server-Side Rendering with hydration enabled (e.g., via provideClientHydration()).
• Hierarchical HttpClient with Delegation: The application configures a child HttpClient using withRequestsMadeViaParent().
• Parent-Level Authentication Injection: Authentication credentials (such as Authorization headers, session cookies, or custom API tokens filtered via withHttpTransferCacheOptions) are attached by an interceptor in the parent injector chain rather than on the initial child request.
• Shared HTML Caching: The SSR HTML responses are cached by a shared caching layer (CDN, reverse proxy, or application-level HTML cache).

Vulnerable Code Pattern Example

// Parent Injector / Application Config
export const appConfig: ApplicationConfig = {
  providers: [
    provideHttpClient(
      // Parent interceptor attaches sensitive Authorization header
      withInterceptors([
        (req, next) => next(req.clone({ setHeaders: { Authorization: `Bearer ${getToken()}` } }))
      ])
    ),
  ],
};

// Child Injector / Feature or Component Config
const childClient = createEnvironmentInjector(
  [
    // Child delegates to parent; TransferCache evaluates req BEFORE parent auth interceptor runs
    provideHttpClient(withRequestsMadeViaParent()),
  ],
  parentInjector
).get(HttpClient);

// Request originates without auth headers -> marked cacheable by child TransferCache
childClient.get('/api/user/profile').subscribe();

Patches

The issue is resolved by updating @angular/common to run root interceptors in the terminal…

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.28, 21.2.20, and 22.1.1, Angular's @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. Exploitation requires provideClientHydration, child provideHttpClient delegation through withRequestsMadeViaParent, parent-level credential injection, and an SSR HTML response shared across users by a CDN, reverse proxy, or application cache. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data. Applications can mitigate by attaching credentials at the child, filtering sensitive endpoints with withHttpTransferCacheOptions, disabling transfer caching for sensitive routes, or marking personalized HTML private or no-store. This issue is fixed in versions 20.3.28, 21.2.20, and 22.1.1.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.28, 21.2.20, and 22.1.1, Angular's @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. Exploitation requires provideClientHydration, child provideHttpClient delegation through withRequestsMadeViaParent, parent-level credential injection, and an SSR HTML response shared across users by a CDN, reverse proxy, or application cache. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data. Applications can mitigate by attaching credentials at the child, filtering sensitive endpoints with withHttpTransferCacheOptions, disabling transfer caching for sensitive routes, or marking personalized HTML private or no-store. This issue is fixed in versions 20.3.28, 21.2.20, and 22.1.1.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.28, 21.2.20, and 22.1.1, Angular's @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. Exploitation requires provideClientHydration, child provideHttpClient delegation through withRequestsMadeViaParent, parent-level credential injection, and an SSR HTML response shared across users by a CDN, reverse proxy, or application cache. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data. Applications can mitigate by attaching credentials at the child, filtering sensitive endpoints with withHttpTransferCacheOptions, disabling transfer caching for sensitive routes, or marking personalized HTML private or no-store. This issue is fixed in versions 20.3.28, 21.2.20, and 22.1.1.