CVE-2026-68945: Angular: Cache-Key Ambiguity in HttpTransferCache Leading to Cross-Request Response Reuse and State Poisoning

Angular's HttpTransferCache caches HTTP requests made during Server-Side Rendering (SSR) so that they can be reused during client-side hydration.

During SSR, HttpTransferCache previously generated identical key material for distinct request parameters when repeated values were present because repeated values were joined with commas:

ts new HttpParams().set('role', 'user,admin') new HttpParams().append('role', 'user').append('role', 'admin')

Both requests previously serialized as role=user,admin, allowing distinct HttpClient requests to produce the same transfer-cache key material.

Impact

In an SSR application, this cache-key ambiguity can make a later security-sensitive HttpClient request receive the response from an earlier semantically different request in the same render. For example, an attacker-influenced scalar-comma request can be cached and then replayed as the response for a trusted repeated-param authorization or data request to the same URL. As a result, Angular's server-rendered output can be based on the wrong backend response because the trusted request is not dispatched. This can lead to:

- State Poisoning: Using incorrect or attacker-influenced cached responses for subsequent application logic. - Cross-Request Response Reuse: Reusing cached responses across requests with semantically different parameters.

Patched Versions

- 22.0.2 - 21.2.19 - 20.3.27

Workarounds

If you cannot upgrade immediately, configure your HttpClient requests to skip transfer caching for sensitive endpoints where repeated parameter keys are used:

ts this.http.get('/api/resource', { transferCache: false });

Alternatively, disable the HTTP transfer cache globally in your application bootstrap config:

ts import { provideClientHydration, withNoHttpTransferCache } from '@angular/platform-browser';

export const appConfig = { providers: [ provideClientHydration( withNoHttpTransferCache() ) ] };

— GitHub