Code Injection (Timing Attack)

critical Web App Scanning Plugin ID 98122

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Synopsis

Description

A modern web application will be reliant on several different programming languages.

These languages can be broken up in two flavours. These are client-side languages (such as those that run in the browser -- like JavaScript) and server-side languages (which are executed by the server -- like ASP, PHP, JSP, etc.) to form the dynamic pages (client-side code) that are then sent to the client.

Because all server-side code should be executed by the server, it should only ever come from a trusted source.

Code injection occurs when the server takes untrusted code (ie. from the client) and executes it.

Cyber-criminals will abuse this weakness to execute arbitrary code on the server, which could result in complete server compromise.

By injecting server-side code that is known to take a specific amount of time to execute, scanner was able to detect time-based code injection. This indicates that proper input sanitisation is not occurring.

Solution

It is recommended that untrusted input is never processed as server-side code.
To validate input, the application should ensure that the supplied value contains only the data that are required to perform the relevant action.
For example, where a username is required, then no non-alpha characters should not be accepted.