CVE-2026-27970

Angular before 20.3.30, 21.2.22, and 22.1.4 has a server-side rendering (SSR) vulnerability in @angular/platform-server. The resolveUrl and parseUrl utilities call String.prototype.trim(), which removes leading Unicode whitespace after a same-origin check, converting a relative path into an attacker-controlled protocol-relative URL, leading to SSRF and credential disclosure.

Angular prior to 20.3.34 and 21.0.3 has the @angular/common HttpClient function xsrfInterceptorFn using a regular expression that does not normalize request URLs the same way as the browser's WHATWG URL parser. With XSRF protection enabled, a mutating HTTP request to an attacker-controlled URL containing backslashes, stripped control characters or spaces, or removable ASCII whitespace can be misclassified as relative and same-origin, causing the interceptor to attach the X-XSRF-TOKEN header before the browser dispatches the request to a cross-origin host.

In Angular prior to 20.3.33, 21.2.25, and 22.2.1, ServerPlatformLocation in server-side rendering checks for protocol-relative URLs before WHATWG URL normalization. A request path containing a popping dot segment followed by multiple slashes can bypass the raw resolveUrl check and normalize to a pathname beginning with two slashes. When Angular SSR detects a mismatch with the router's final location, it can place that pathname in an HTTP Location header, causing a browser to navigate to an attacker-controlled origin. Affected applications use @angular/platform-server and @angular/ssr and either expose compatible parameter or child route shapes or pass user-controlled navigation targets through infrastructure that preserves the relevant dot segments or semicolons. Pure client-side SPAs are not affected.

A vulnerability in @angular/router during Node.js server-side rendering allows an unauthenticated remote attacker to send crafted requests with multiple unconfigured empty-path outlet groups. This repeatedly evaluates route configuration, constructs duplicate ActivatedRouteSnapshot trees, executes canMatch guards and resolvers, and can exhaust the Node.js heap or CPU, terminating the SSR worker. The issue is fixed in versions 20.3.33, 21.2.25, and 22.2.1.

In Angular versions from 21.2.0 until 21.2.25 and 22.2.1, RouterLink directives rendered during Node.js server-side rendering retain computed UrlTree instances for the lifetime of each request. When queryParamsHandling is set to merge or preserve, each rendered link can retain a copy of attacker-controlled query parameters, and with oversized query strings this can exhaust the Node.js old-space heap and terminate the SSR worker. The issue is fixed in versions 21.2.25 and 22.2.1.

Prior to 20.3.32, 21.2.24, and 22.2.0, the @angular/router URL parser stores numeric matrix parameter names and numeric outlet names as properties on initially empty JavaScript objects during Node.js server-side rendering. V8 can interpret these URL-derived keys as array indices and allocate dense backing stores sized to high numeric values, so repeated small path segments cause disproportionate per-segment heap consumption. An unauthenticated attacker can send overlapping requests containing repeated numeric matrix parameters when SSR is enabled, the router directly parses the request URL, and upstream proxies allow semicolons and multiple path segments, eventually exhausting the Node.js old-space heap and terminating the SSR worker. Pure client-side Angular applications are not affected.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.31, 21.2.23, and 22.1.6, the @angular/platform-server DOM emulation parser can enter an infinite synchronous loop when Angular server-side rendering processes attacker-controlled HTML containing an incomplete DOCTYPE that ends with whitespace at end of input. In Domino lib/HTMLParser.js, after_doctype_name_state emits doctype and EOF tokens without advancing nextchar or leaving the fixed-lookahead state, so the scanner repeatedly handles the same EOF marker. A remote unauthenticated attacker can use this condition through server-side HTML parsing paths such as innerHTML binding to consume a Node.js SSR worker at full CPU, starve the event loop, and stop concurrent and subsequent requests. This issue is fixed in versions 20.3.31, 21.2.23, and 22.1.6.

Angular before 20.3.30, 21.2.22, and 22.1.4 has a server-side rendering (SSR) vulnerability in @angular/platform-server. Serialization of untrusted input inside fallback raw-content elements (noscript, iframe, noembed, noframes) fails to escape matching closing tags, enabling arbitrary JavaScript execution.

In Angular prior to 20.3.28, 21.2.20, and 22.1.1, @angular/common HttpTransferCache can cache an authenticated response when Server-Side Rendering (SSR) and hydration use a hierarchical HttpClient configured with withRequestsMadeViaParent. The child TransferCache evaluates an initially anonymous request before delegation, then a parent withInterceptors chain adds an Authorization header, cookie, or API token; although the parent cache skips the authenticated request, the child still stores the private response in TransferState serialized as JSON in the ng-state script. A later unauthenticated or unauthorized visitor can receive the cached HTML containing the earlier authenticated user's sensitive response data.

Angular before 20.3.30, 21.2.22, and 22.1.4 has a server-side rendering (SSR) vulnerability in @angular/platform-server. Serialization of ProcessingInstruction DOM nodes inside fallback raw-content elements fails to escape matching ancestor closing tags, allowing premature container termination and arbitrary JavaScript execution.