@angular/common: Denial of Service (DoS) via OOM in Number Formatting (digitsInfo)

A Denial of Service (DoS) vulnerability exists in the @angular/common package of Angular. The formatNumber function, which is also utilized by DecimalPipe, PercentPipe, and CurrencyPipe, does not properly validate the upper bounds of the digitsInfo parameter. Specifically, the minimum and maximum fraction digits parsed from the digitsInfo string (e.g., 1.2-4) are converted to integers and used without limits.

When parsing a maliciously crafted digitsInfo string with excessively large fraction digit values (e.g., 1.200000000-200000000), the internal roundNumber function attempts to pad the digits array to match the requested fraction size. This results in an unbounded loop that repeatedly pushes elements into an array.

Impact

Successful exploitation of this vulnerability allows an attacker to trigger resource exhaustion, leading to a Denial of Service (DoS):

• Server-Side Rendering (SSR): In applications using SSR (e.g., @angular/ssr), an attacker can crash the Node.js server process due to a JavaScript heap out of memory error. This affects the availability of the application for all users.
• Client-Side Rendering (CSR): In standard client-side applications, the unbounded loop will block the main thread, freezing the user's browser tab and making it unresponsive.

Attack Preconditions

For this vulnerability to be exploitable, the following conditions must be met:

1. Vulnerable Component Usage: The application must use Angular's number formatting utilities, such as the formatNumber function directly, or via template pipes (DecimalPipe, PercentPipe, CurrencyPipe).
2. Attacker-Controlled Parameter: The digitsInfo parameter passed to these utilities must be customizable or directly controlled by untrusted user input (e.g., parsed from query parameters, user preference settings, or API responses that accept user-defined formatting options). If digitsInfo is trusted or limited to a known, defined range for its value, the vulnerability is not exploitable by external attackers.

Patches

• 22.0.0-rc.2
• 21.2.15
• 20.3.22
• 19.2.23

Credits

This vulnerability was discovered and reported by CodeMender from Google DeepMind.