Summary
@angular/platform-server: Open Redirect via Protocol-Relative URLs in Server-Side Rendering (SSR)
An open redirect vulnerability was identified in @angular/platform-server when Server-Side Rendering (SSR) is enabled.
When Angular SSR renders an incoming request, URL resolution and platform navigation are managed by ServerPlatformLocation using resolveUrl (or parseUrl in v20). While resolveUrl rejected protocol-relative URLs whose raw string directly started with //, this check ran prior to WHATWG URL normalization.
When a request URL includes a popping dot-segment followed by multiple slashes (such as /.//evil.test or serialized from router route shapes like /.;/(//evil.test)), the input bypassed the initial urlStr.startsWith('//') check. Subsequent WHATWG URL parsing resolved the dot-segments and resulted in a pathname starting with // (//evil.test).
Consequently, ServerPlatformLocation stored pathname = '//evil.test'. When @angular/ssr detected a mismatch between the rendered URL and the router's final location state, it emitted the unnormalized pathname into the HTTP Location response header, producing an HTTP 302 redirect with Location: //evil.test, which browsers resolve as a protocol-relative navigation off-origin.
Attack Preconditions & Vulnerable Configurations
An application is affected if the following conditions are met:
- SSR Enabled: The application runs in a Server-Side Rendering environment using
@angular/platform-serverand@angular/ssr. - Parameter Route Shapes: The router contains parameter routes with wildcard or child segments (e.g.
/:tenantmatching.and serializing secondary outlet groups(//evil.test)to/.//evil.test), or passes user-provided navigation targets (e.g.returnUrl). - Reverse Proxy Passthrough: Upstream reverse proxies (Nginx, Cloudflare, ALB) pass semicolons (
;) or dot-segments without stripping or normalizing them.
Exploit Payload Example
An attacker sends a request targeting a route with parameters and child segments:
GET /.;/(//evil.test) HTTP/1.1
Host: example.com
Response:
HTTP/1.1 302 Found
Location: //evil.test
The client browser resolves //evil.test protocol-relatively and redirects the user away from example.com to evil.test.
Workarounds & Mitigations
If you cannot immediately upgrade to a patched version, apply one of the following mitigations at your edge reverse proxy or WAF:
- Reject Paths with Dot-Segments Followed by Slashes:
Configure your reverse proxy (e.g., Nginx, Cloudflare, AWS WAF) to block requests containing/.//,/..//, or/.;/:# Nginx example: reject suspicious path normalization sequences if ($request_uri ~* "(\n/\.\/|\/\.\;)") { return 400; } - Sanitize Redirect Headers:
Ensure edge proxies or API gateways rewrite or disallow protocol-relative (//)Locationresponse headers originating from the SSR upstream.
Impact
Successful exploitation allows an unauthenticated remote attacker to craft URLs that trick Angular SSR into redirecting users to an arbitrary external domain.
- Bypasses Application-Level Guards: Common application-level validation routines (such as checking
!returnUrl.startsWith('//')before invokingrouter.navigateByUrl) accept/.//evil.testor/.;/(//evil.test)as a safe relative path, allowing attackers to bypass redirect allowlists. - Client-side SPAs Unaffected: Pure client-side Angular applications (Single Page Applications without SSR) are not vulnerable, as
ServerPlatformLocationis only utilized in server-side execution environments.
Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The issue is resolved by updating resolveUrl (and parseUrl in v20) in @angular/platform-server to verify that the normalized URL pathname does not start with // when allowProtocolRelative is false.
22.2.121.2.2520.3.33
Frequently Asked Questions
- What is CVE-2026-111754? CVE-2026-111754 is a medium-severity open redirect vulnerability in @angular/platform-server (npm), affecting versions >= 22.0.0, < 22.2.1. It is fixed in 22.2.1, 21.2.25, 20.3.33. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
- Which versions of @angular/platform-server are affected by CVE-2026-111754? @angular/platform-server (npm) versions >= 22.0.0, < 22.2.1 is affected.
- Is there a fix for CVE-2026-111754? Yes. CVE-2026-111754 is fixed in 22.2.1, 21.2.25, 20.3.33. Upgrade to this version or later.
- Is CVE-2026-111754 exploitable, and should I be worried? Whether CVE-2026-111754 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-111754 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-111754?
- Upgrade
@angular/platform-serverto 22.2.1 or later - Upgrade
@angular/platform-serverto 21.2.25 or later - Upgrade
@angular/platform-serverto 20.3.33 or later
- Upgrade