CWE-457—Use of Uninitialized Variable

Weakness Name

Use of Uninitialized Variable

Description

The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

In some languages such as C and C++, stack variables are not initialized by default. They generally contain junk data with the contents of stack memory before the function was invoked. An attacker can sometimes control or read these contents. In other languages or conditions, a variable that is not explicitly initialized can be given a default value that has security implications, depending on the logic of the program. The presence of an uninitialized variable can sometimes indicate a typographic error in the code.

Common Consequences

Scope:

Availability, Integrity, Other

Impact:

Other

Notes:

Initial variables usually contain junk, which can not be trusted for consistency. This can lead to denial of service conditions, or modify control flow in unexpected ways. In some cases, an attacker can "pre-initialize" the variable using previous actions, which might enable code execution. This can cause a race condition if a lock variable check passes when it should not.

Scope:

Authorization, Other

Impact:

Other

Notes:

Strings that are not initialized are especially dangerous, since many functions expect a null at the end -- and only at the end -- of a string.

Related Weaknesses

• CWE-665Improper InitializationMedium
• CWE-908Use of Uninitialized ResourceMedium