CWE-839: Numeric Range Comparison Without Minimum Check
Description
The product checks a value to ensure that it is less than or equal to a maximum, but it does not also verify that the value is greater than or equal to the minimum.
Some products use signed integers or floats even when their values are only expected to be positive or 0. An input validation check might assume that the value is positive, and only check for the maximum value. If the value is negative, but the code assumes that the value is positive, this can produce an error. The error may have security consequences if the negative value is used for memory allocation, array access, buffer access, etc. Ultimately, the error could lead to a buffer overflow or other type of memory corruption. The use of a negative number in a positive-only context could have security implications for other types of resources. For example, a shopping cart might check that the user is not requesting more than 10 items, but a request for -3 items could cause the application to calculate a negative price and credit the attacker's account.
- Abstraction
- BaseA weakness specific enough to point to detection and prevention methods.
- Likelihood of exploit
- Not rated by MITRE
- Status
- Incomplete
Common consequences
- IntegrityConfidentialityAvailability
Modify Application Data; Execute Unauthorized Code or Commands
An attacker could modify the structure of the message or data being sent to the downstream component, possibly injecting commands.
- Availability
DoS: Resource Consumption (Other)
in some contexts, a negative value could lead to resource consumption.
- ConfidentialityIntegrity
Modify Memory; Read Memory
If a negative value is used to access memory, buffers, or other indexable structures, it could access memory outside the bounds of the buffer.
Potential mitigations
- ImplementationEnforcement by Conversion
If the number to be used is always expected to be positive, change the variable type from signed to unsigned or size_t.
- ImplementationInput Validation
If the number to be used could have a negative value based on the specification (thus requiring a signed value), but the number should only be positive to preserve code correctness, then include a check to ensure that the value is positive.
Related weaknesses
CAPEC attack patterns that exploit it
CWE 4.20 links no CAPEC attack pattern to this weakness.