CVE-2025-66035

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to versions 19.2.16, 20.3.14, and 21.0.1, there is a XSRF token leakage via protocol-relative URLs in angular HTTP clients. The vulnerability is a Credential Leak by App Logic that leads to the unauthorized disclosure of the Cross-Site Request Forgery (XSRF) token to an attacker-controlled domain. Angular's HttpClient has a built-in XSRF protection mechanism that works by checking if a request URL starts with a protocol (http:// or https://) to determine if it is cross-origin. If the URL starts with protocol-relative URL (//), it is incorrectly treated as a same-origin request, and the XSRF token is automatically added to the X-XSRF-TOKEN header. This issue has been patched in versions 19.2.16, 20.3.14, and 21.0.1. A workaround for this issue involves avoiding using protocol-relative URLs (URLs starting with //) in HttpClient requests. All backend communication URLs should be hardcoded as relative paths (starting with a single /) or fully qualified, trusted absolute URLs.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to versions 19.2.16, 20.3.14, and 21.0.1, there is a XSRF token leakage via protocol-relative URLs in angular HTTP clients. The vulnerability is a Credential Leak by App Logic that leads to the unauthorized disclosure of the Cross-Site Request Forgery (XSRF) token to an attacker-controlled domain. Angular's HttpClient has a built-in XSRF protection mechanism that works by checking if a request URL starts with a protocol (http:// or https://) to determine if it is cross-origin. If the URL starts with protocol-relative URL (//), it is incorrectly treated as a same-origin request, and the XSRF token is automatically added to the X-XSRF-TOKEN header. This issue has been patched in versions 19.2.16, 20.3.14, and 21.0.1. A workaround for this issue involves avoiding using protocol-relative URLs (URLs starting with //) in HttpClient requests. All backend communication URLs should be hardcoded as relative paths (starting with a single /) or fully qualified, trusted absolute URLs.

The vulnerability is a **Credential Leak by App Logic** that leads to the **unauthorized disclosure of the Cross-Site Request Forgery (XSRF) token** to an attacker-controlled domain. Angular's HttpClient has a built-in XSRF protection mechanism that works by checking if a request URL starts with a protocol (`http://` or `https://`) to determine if it is cross-origin. If the URL starts with protocol-relative URL (`//`), it is incorrectly treated as a same-origin request, and the XSRF token is automatically added to the `X-XSRF-TOKEN` header. ### Impact The token leakage completely bypasses Angular's built-in CSRF protection, allowing an attacker to capture the user's valid XSRF token. Once the token is obtained, the attacker can perform arbitrary Cross-Site Request Forgery (CSRF) attacks against the victim user's session. ### Attack Preconditions 1. The victim's Angular application must have **XSRF protection enabled**. 2. The attacker must be able to make the application send a state-changing HTTP request (e.g., `POST`) to a **protocol-relative URL** (e.g., `//attacker.com`) that they control. ### Patches - 19.2.16 - 20.3.14 - 21.0.1 ### Workarounds Developers should avoid using protocol-relative URLs (URLs starting with `//`) in HttpClient requests. All backend communication URLs should be hardcoded as relative paths (starting with a single `/`) or fully qualified, trusted absolute URLs.

The vulnerability is a **Credential Leak by App Logic** that leads to the **unauthorized disclosure of the Cross-Site Request Forgery (XSRF) token** to an attacker-controlled domain. Angular's HttpClient has a built-in XSRF protection mechanism that works by checking if a request URL starts with a protocol (`http://` or `https://`) to determine if it is cross-origin. If the URL starts with protocol-relative URL (`//`), it is incorrectly treated as a same-origin request, and the XSRF token is automatically added to the `X-XSRF-TOKEN` header. ### Impact The token leakage completely bypasses Angular's built-in CSRF protection, allowing an attacker to capture the user's valid XSRF token. Once the token is obtained, the attacker can perform arbitrary Cross-Site Request Forgery (CSRF) attacks against the victim user's session. ### Attack Preconditions 1. The victim's Angular application must have **XSRF protection enabled**. 2. The attacker must be able to make the application send a state-changing HTTP request (e.g., `POST`) to a **protocol-relative URL** (e.g., `//attacker.com`) that they control. ### Patches - 19.2.16 - 20.3.14 - 21.0.1 ### Workarounds Developers should avoid using protocol-relative URLs (URLs starting with `//`) in HttpClient requests. All backend communication URLs should be hardcoded as relative paths (starting with a single `/`) or fully qualified, trusted absolute URLs.