CWE-197: Numeric Truncation Error
Official CWE-197 CWE context with Glexia analysis, remediation guidance, related CVEs, and ATT&CK context.
Glexia's Take
CWE-197: Numeric Truncation Error
Numeric Truncation Error represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Integrity: Modify Memory: The true value of the data is lost and corrupted data is used.
Developer Pattern
CWE-197 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Confidence
high confidence from CWE-197, 4.20.
Official CWE Definition
CWE-197: Numeric Truncation Error
Truncation errors occur when a primitive is cast to a primitive of a smaller size and data is lost in the conversion.
When a primitive is cast to a smaller primitive, the high order bits of the large value are lost in the conversion, potentially resulting in an unexpected value that is not equal to the original value. This value may be required as an index into a buffer, a loop iterator, or simply necessary state data. In any case, the value cannot be trusted and the system will be in an undefined state. While this method may be employed viably to isolate the low bits of a value, this usage is rare, and truncation usually implies that an implementation error has occurred.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- This example, while not exploitable, shows the possible mangling of values associated with truncation errors: The above code, when compiled and run on certain systems, returns the following output:,This problem may be exploitable when the truncated value is used as an array index, which can happen implicitly when 64-bit values are used as indexes, as they are truncated to 32 bits.
- In the following Java example, the method updateSalesForProduct is part of a business application class that updates the sales information for a particular product. The method receives as arguments the product ID and the integer amount sold. The product ID is used to retrieve the total product count from an inventory object which returns the count as an integer. Before calling the method of the sales object to update the sales count the integer values are converted to The primitive type short since the method requires short type for the method arguments. However, a numeric truncation error can occur if the integer values are higher than the maximum value allowed for the primitive type short. This can cause unexpected results or loss or corruption of data. In this case the sales database may be corrupted with incorrect data. Explicit casting from a from a larger size primitive type to a smaller size primitive type should be prevented. The following example an if statement is added to validate that the integer values less than the maximum value for the primitive type short before the explicit cast and the call to the sales method.
Remediation
- Implementation: Ensure that no casts, implicit or explicit, take place that move from a larger size primitive or a smaller size primitive.
Detection
- Fuzzing: Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
- Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
- CWE-192: Integer Coercion Error
- CWE-194: Unexpected Sign Extension
- CWE-195: Signed to Unsigned Conversion Error
- CWE-196: Unsigned to Signed Conversion Error
- CWE-681: Incorrect Conversion between Numeric Types
- CWE-681: Incorrect Conversion between Numeric Types
- CWE-681: Incorrect Conversion between Numeric Types
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.