CVE-2026-54266: @angular/common: Weak 32-Bit Cache Key Hashing in `HttpTransferCache` Leading to Cross-Request Data Leakage 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. This avoids repeating the same HTTP requests on the client. The cached responses are stored in TransferState using a cache key generated by hashing request properties (method, response type, mapped URL, serialized body, and sorted query parameters).

The cache keys are generated using a weak 32-bit DJB2-like polynomial rolling hash. The 32-bit hash space is extremely small, allowing attackers to find hash collisions.

An attacker can easily find a query parameter string (e.g., q=aaCAZMMM for a search request) that produces the exact same 32-bit hash as a sensitive endpoint (e.g., /api/user/profile). When a victim visits a crafted link containing the colliding parameter, the SSR process executes both the search request and the profile request. Due to the hash collision, the search response overwrites the profile response in the TransferState cache.