CWE-196
Unsigned to Signed Conversion Error
Description
The product uses an unsigned primitive and performs a cast to a signed primitive, which can produce an unexpected value if the value of the unsigned primitive can not be represented using a signed primitive.
Although less frequent an issue than signed-to-unsigned conversion, unsigned-to-signed conversion can be the perfect precursor to dangerous buffer underwrite conditions that allow attackers to move down the stack where they otherwise might not have access in a normal buffer overflow condition. Buffer underwrites occur frequently when large unsigned values are cast to signed values, and then used as indexes into a buffer or for pointer arithmetic.
Parent Weaknesses (ChildOf)
Related Weaknesses
Common Consequences
Scope
Impact
DoS: Crash, Exit, or Restart
Scope
Impact
Modify Memory
Scope
Impact
Execute Unauthorized Code or Commands, Bypass Protection Mechanism
Potential Mitigations
Choose a language which is not subject to these casting flaws.
Design object accessor functions to implicitly check values for valid sizes. Ensure that all functions which will be used as a size are checked previous to use as a size. If the language permits, throw exceptions rather than using in-band errors.
Error check the return values of all functions. Be aware of implicit casts made, and use unsigned variables for sizes if at all possible.
Applicable Platforms
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