Angular: Denial of Service via Unmatched Empty-Path Outlet Route Matching in Server-Side Rendering (SSR)

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.33, 21.2.25, and 22.2.1, @angular/router in Node.js server-side rendering fails to require auxiliary outlet URL segments to match routes configured for their outlet names. Crafted requests containing multiple unconfigured empty-path outlet groups can repeatedly evaluate the route configuration, construct duplicate ActivatedRouteSnapshot trees, execute canMatch guards and resolvers, and copy route parameters and queryParams for each outlet. An unauthenticated remote attacker can exhaust the Node.js heap or CPU and terminate an SSR worker when SSR is enabled, a route level contains an empty-path route or named outlet, upstream infrastructure forwards the request target, and the worker has a constrained heap. The allocation is transient rather than a persistent leak, and client-side SPAs and build-time prerendering are not affected. This issue is fixed in versions 20.3.33, 21.2.25, and 22.2.1.

Source published

3 Nov 2026 20:52:16 UTC

Source modified

3 Nov 2026 20:52:16 UTC

Observed here

3 Nov 2026 22:57:17 UTC

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CVSS 4.0 · 8.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N