CWE-621: Variable Extraction Error

Description

The product uses external input to determine the names of variables into which information is extracted, without verifying that the names of the specified variables are valid. This could cause the program to overwrite unintended variables.

Submission Date :

May 7, 2007, midnight

Modification Date :

2023-10-26 00:00:00+00:00

Organization :

MITRE

Extended Description

For example, in PHP, extraction can be used to provide functionality similar to register_globals, a dangerous functionality that is frequently disabled in production systems. Calling extract() or import_request_variables() without the proper arguments could allow arbitrary global variables to be overwritten, including superglobals.

Similar functionality is possible in other interpreted languages, including custom languages.

Example Vulnerable Codes

Example - 1

This code uses the credentials sent in a POST request to login a user.

// //Log user in, and set $isAdmin to true if user is an administrator// 

$isAdmin = true;$query = buildQuery($user,$pass);mysql_query($query);if(getUserRole($user) == "Admin"){}
function login($user,$pass){}$isAdmin = false;extract($_POST);login(mysql_real_escape_string($user),mysql_real_escape_string($pass));

The call to extract() will overwrite the existing values of any variables defined previously, in this case $isAdmin. An attacker can send a POST request with an unexpected third value "isAdmin" equal to "true", thus gaining Admin privileges.

Related Weaknesses

This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined to give an overview of the different insight to similar items that may exist at higher and lower levels of abstraction.

CWE-471: Modification of Assumed-Immutable Data (MAID)

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CWE-914: Improper Control of Dynamically-Identified Variables

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