Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 22.0.0-rc.2, 21.2.15, 20.3.22, and 19.2.23, an issue in the @angular/platform-server package allows remote attackers to bypass host allowlist constraints and direct server-side outgoing requests to arbitrary external endpoints. This occurs due to a parser differential between the strict WHATWG URL parser used for allowlist validation and the lenient Domino URL parser used to initialize the server emulated DOM. When a server-side request contains a malformed URL with a double port structure (e.g., http://evil.com:80:80/path), Node's strict URL.canParse(url) logic returns false and skips host check validation entirely. However, the same malformed URL is later accepted and parsed leniently by Domino's internal parser, which resolves the origin to http://evil.com:80. The Angular SSR HTTP request interceptor (relativeUrlsTransformerInterceptorFn) then resolves all relative backend HTTP requests against this adopted origin, executing the SSRF attack. This vulnerability is fixed in 22.0.0-rc.2, 21.2.15, 20.3.22, and 19.2.23.

Affected: npm: @angular/platform-server

An issue in the `@angular/platform-server` package allows remote attackers to bypass host allowlist constraints and direct server-side outgoing requests to arbitrary external endpoints. This occurs due to a parser differential between the strict WHATWG URL parser used for allowlist validation and the lenient Domino URL parser used to initialize the server emulated DOM.

When a server-side request contains a malformed URL with a double port structure (e.g., `http://evil.com:80:80/path`), Node's strict `URL.canParse(url)` logic returns `false` and skips host check validation entirely. However, the same malformed URL is later accepted and parsed leniently by Domino's internal parser, which resolves the origin to `http://evil.com:80`. The Angular SSR HTTP request interceptor (`relativeUrlsTransformerInterceptorFn`) then resolves all relative backend HTTP requests against this adopted origin, executing the SSRF attack.

### Impact

Any Angular application utilizing server-side rendering (`@angular/platform-server`) that configures host routing allowlists (`allowedHosts`) is vulnerable to this allowlist bypass.

By sending an HTTP request with a malformed Host header (e.g. `Host: evil.com:80:80`) or an absolute-form request URI, an attacker can bypass the allowlist logic completely (even when configured with a strict default deny setup). The SSR application will then route all relative `HttpClient` outgoing API queries—which commonly carry sensitive credentials, session cookies,…

Affected: Ubuntu:Pro:16.04:LTS: angular.js, Ubuntu:Pro:18.04:LTS: angular.js, Ubuntu:Pro:20.04:LTS: angular.js, Ubuntu:22.04:LTS: angular.js, Ubuntu:24.04:LTS: angular.js, Ubuntu:25.10: angular.js, Ubuntu:26.04:LTS: angular.js

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 22.0.0-rc.2, 21.2.15, 20.3.22, and 19.2.23, an issue in the @angular/platform-server package allows remote attackers to bypass host allowlist constraints and direct server-side outgoing requests to arbitrary external endpoints. This occurs due to a parser differential between the strict WHATWG URL parser used for allowlist validation and the lenient Domino URL parser used to initialize the server emulated DOM. When a server-side request contains a malformed URL with a double port structure (e.g., http://evil.com:80:80/path), Node's strict URL.canParse(url) logic returns false and skips host check validation entirely. However, the same malformed URL is later accepted and parsed leniently by Domino's internal parser, which resolves the origin to http://evil.com:80. The Angular SSR HTTP request interceptor (relativeUrlsTransformerInterceptorFn) then resolves all relative backend HTTP requests against this adopted origin, executing the SSRF attack. This vulnerability is fixed in 22.0.0-rc.2, 21.2.15, 20.3.22, and 19.2.23.

Ein Angreifer kann mehrere Schwachstellen in Angular ausnutzen, um erweiterte Berechtigungen zu erlangen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Cross-Site-Scripting-Angriffe durchzuführen, einen Denial-of-Service-Zustand herbeizuführen, Daten zu manipulieren oder offenzulegen, Benutzer auf bösartige Websites umzuleiten oder Sitzungen zu kapern.