CWE-195 - Signed to Unsigned Conversion Error

CWE ID:

CWE-195

Abstraction:Variant
Structure:Simple
Status:Draft

Release Date:2006-07-19
Latest Modification Date:2023-06-29

Weakness Name

Signed to Unsigned Conversion Error

Description

The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.

It is dangerous to rely on implicit casts between signed and unsigned numbers because the result can take on an unexpected value and violate assumptions made by the program. Often, functions will return negative values to indicate a failure. When the result of a function is to be used as a size parameter, using these negative return values can have unexpected results. For example, if negative size values are passed to the standard memory copy or allocation functions they will be implicitly cast to a large unsigned value. This may lead to an exploitable buffer overflow or underflow condition.

Common Consequences

Scope: Integrity

Impact: Unexpected State

Notes: Conversion between signed and unsigned values can lead to a variety of errors, but from a security standpoint is most commonly associated with integer overflow and buffer overflow vulnerabilities.