COMMON WEAKNESS ENUMERATIONIncomplete

CWE-621

Variable Extraction Error

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.

Abstraction

Variant

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

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.

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.

Terminology

Alternate terms and usages

Variable overwrite

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Modify Application Data

Affected security scopes: Integrity

An attacker could modify sensitive data or program variables.

Defence

How is it prevented and fixed?

Implementation

Input Validation

Detail
Use allowlists of variable names that can be extracted.

Implementation

Refactoring

Detail
Consider refactoring your code to avoid extraction routines altogether.

Implementation

Implementation-phase defence

Detail
In PHP, call extract() with options such as EXTR_SKIP and EXTR_PREFIX_ALL; call import_request_variables() with a prefix argument. Note that these capabilities are not present in all PHP versions.
CWE-621: Common Weakness Enumeration Entry CWE-621 · DayBreach Sözlük · DayBreach