190

DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability

Execute Unauthorized Code or Commands; Bypass Protection Mechanism

Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)

Bypass Protection Mechanism

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

If possible, choose a language or compiler that performs automatic bounds checking.

Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [ REF-1482 ].

Use libraries or frameworks that make it easier to handle numbers without unexpected consequences.

Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++). [ REF-106 ]

Strategy: Input Validation

Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.

Use unsigned integers where possible. This makes it easier to perform validation for integer overflows. When signed integers are required, ensure that the range check includes minimum values as well as maximum values.

Understand the programming language's underlying representation and how it interacts with numeric calculation ( CWE-681 ). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how the language handles numbers that are too large or too small for its underlying representation. [ REF-7 ]

Also be careful to account for 32-bit, 64-bit, and other potential differences that may affect the numeric representation.

Architecture and Design

Strategy: Compilation or Build Hardening

Class: Not Language-Specific (Undetermined Prevalence)

Class: Not Technology-Specific (Undetermined Prevalence)

The following image processing code allocates a table for images.

This code intends to allocate a table of size num_imgs, however as num_imgs grows large, the calculation determining the size of the list will eventually overflow ( CWE-190 ). This will result in a very small list to be allocated instead. If the subsequent code operates on the list as if it were num_imgs long, it may result in many types of out-of-bounds problems ( CWE-119 ).

The following code excerpt from OpenSSH 3.3 demonstrates a classic case of integer overflow:

If nresp has the value 1073741824 and sizeof(char*) has its typical value of 4, then the result of the operation nresp*sizeof(char*) overflows, and the argument to xmalloc() will be 0. Most malloc() implementations will happily allocate a 0-byte buffer, causing the subsequent loop iterations to overflow the heap buffer response.

Integer overflows can be complicated and difficult to detect. The following example is an attempt to show how an integer overflow may lead to undefined looping behavior:

In the above case, it is entirely possible that bytesRec may overflow, continuously creating a lower number than MAXGET and also overwriting the first MAXGET-1 bytes of buf.

In this example the method determineFirstQuarterRevenue is used to determine the first quarter revenue for an accounting/business application. The method retrieves the monthly sales totals for the first three months of the year, calculates the first quarter sales totals from the monthly sales totals, calculates the first quarter revenue based on the first quarter sales, and finally saves the first quarter revenue results to the database.

However, in this example the primitive type short int is used for both the monthly and the quarterly sales variables. In C the short int primitive type has a maximum value of 32768. This creates a potential integer overflow if the value for the three monthly sales adds up to more than the maximum value for the short int primitive type. An integer overflow can lead to data corruption, unexpected behavior, infinite loops and system crashes. To correct the situation the appropriate primitive type should be used, as in the example below, and/or provide some validation mechanism to ensure that the maximum value for the primitive type is not exceeded.

Note that an integer overflow could also occur if the quarterSold variable has a primitive type long but the method calculateRevenueForQuarter has a parameter of type short.

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.