Request Credential & Cache Policy Stripping in Angular Service Worker

An issue in the `@angular/service-worker` package compromises the integrity of request-policy enforcement during request reconstruction. When the Angular Service Worker intercepts network requests for matched assets, it reconstructs a new `Request` object using an internal helper function. During this reconstruction process, the helper function strips explicit client-defined safety parameters: the credentials configuration (such as `credentials: 'omit'`) and the HTTP `cache` mode configuration (such as `cache: 'no-store'`). These are reverted back to standard browser-default parameters (`credentials: 'same-origin'` and default HTTP cache properties). This causes the browser to include active credentials (such as cookies or Authorization headers) on outbound requests where the client-side developer explicitly instructed they should be omitted, leading to potential session leaks. Additionally, it causes private or non-cacheable resources to be cached by the service worker's engine, making private page states accessible or persistent inside the client's local cache post-logout. ### Impact Web applications registering the `@angular/service-worker` package are vulnerable to credential exposure or post-logout cache persistence if client-side code relies on fetch calls with explicit safety attributes (such as `{ credentials: 'omit' }` or `{ cache: 'no-store' }`) targeting paths matched by service worker asset groups. By stripping these safety boundaries, the service worker exposes same-origin cookies and dynamic sensitive data to endpoints that should not receive them, or retains dynamic user sessions in cache storage where logout operations fail to fully evict user records. ### Attack Preconditions To successfully exploit this vulnerability, all of the following application states and parameters must concurrently exist: 1. **Active Angular Service Worker:** The target application uses `@angular/service-worker` and has an active registration of `ngsw-worker.js` inside the client's browser context. 2. **Asset Group Matching:** An `assetGroups` pattern in `ngsw-config.json` encompasses the target dynamic routing endpoint. 3. **Established User Session:** The victim user currently has an active authentication state, such as valid same-origin session cookies or auth headers stored by the browser. 4. **Client-Side Safe Fetch Call:** The application initiates an explicit fetch request to the route with safety parameters: `{ credentials: 'omit' }` or specific cache control parameters (e.g. `{ cache: 'no-store' }`). ### Mitigations & Workarounds If upgrading the `@angular/service-worker` package is not immediately feasible, developers should implement the following defensive measures: * **Strict Cookie Configuration:** Apply strict flags to session cookies (`SameSite=Strict; Secure; HttpOnly`) and ensure complete route isolation for credential-guarded secure resources. * **Exclude Secure Endpoints from SW Config:** Ensure that patterns targeting dynamic, secure endpoints are explicitly excluded from automatic asset groups or caching scopes in your `ngsw-config.json`. * **Post-Logout Cache Invalidation:** Programmatically purge the browser's Cache Storage API entries registered by the Angular Service Worker upon user logout: ```javascript if ('caches' in window) { caches.keys().then(names => { for (let name of names) { if (name.startsWith('ngsw:')) { caches.delete(name); } } }); } ``` ### Patches - 22.0.0-rc.2 - 21.2.15 - 20.3.22 - 19.2.23 ### References - https://github.com/angular/angular/pull/68904

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