Description
The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.
When product performs a security-critical calculation incorrectly, it might lead to incorrect resource allocations, incorrect privilege assignments, or failed comparisons among other things. Many of the direct results of an incorrect calculation can lead to even larger problems such as failed protection mechanisms or even arbitrary code execution.
Potential Impact
Availability
DoS: Crash, Exit, or Restart
Integrity, Confidentiality, Availability
DoS: Crash, Exit, or Restart, DoS: Resource Consumption (Other), Execute Unauthorized Code or Commands
Access Control
Gain Privileges or Assume Identity
Access Control
Bypass Protection Mechanism
Demonstrative Examples
img_t table_ptr; /*struct containing img data, 10kB each*/int num_imgs;...num_imgs = get_num_imgs();table_ptr = (img_t*)malloc(sizeof(img_t)*num_imgs);......int touchdowns = team.getTouchdowns();int yardsGained = team.getTotalYardage();System.out.println(team.getName() + " averages " + yardsGained / touchdowns + "yards gained for every touchdown scored");...int *p = x;char * second_char = (char *)(p + 1);Mitigations & Prevention
Understand your programming language's underlying representation and how it interacts with numeric calculation. Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how your language handles numbers that are too large or too small for its underlying representation.
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 the appropriate type for the desired action. For example, in C/C++, only use unsigned types for values that could never be negative, such as height, width, or other numbers related to quantity.
Use languages, 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++).
Use languages, 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++).
Examine compiler warnings closely and eliminate problems with potential security implications, such as signed / unsigned mismatch in memory operations, or use of uninitialized variables. Even if the weakness is rarely exploitable, a single failure may lead to the compromise of the entire system.
Detection Methods
- Manual Analysis High — This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. Specifically, manual static analysis is useful for eval
- 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 sea
- Fuzzing High — 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,
Real-World CVE Examples
| CVE ID | Description |
|---|---|
| CVE-2020-0022 | chain: mobile phone Bluetooth implementation does not include offset when calculating packet length (CWE-682), leading to out-of-bounds write (CWE-787) |
| CVE-2010-1378 | Chain: incorrect calculation (CWE-682) allows attackers to bypass certificate checks (CWE-295) |
| CVE-2004-1363 | substitution overflow: buffer overflow using environment variables that are expanded after the length check is performed |
Related Weaknesses
Taxonomy Mappings
- CERT C Secure Coding: FLP32-C — Prevent or detect domain and range errors in math functions
- CERT C Secure Coding: INT07-C — Use only explicitly signed or unsigned char type for numeric values
- CERT C Secure Coding: INT13-C — Use bitwise operators only on unsigned operands
- CERT C Secure Coding: INT33-C — Ensure that division and remainder operations do not result in divide-by-zero errors
- CERT C Secure Coding: INT34-C — Do not shift an expression by a negative number of bits or by greater than or equal to the number of bits that exist in the operand
Frequently Asked Questions
What is CWE-682?
CWE-682 (Incorrect Calculation) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Pillar-level weakness. The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.
How can CWE-682 be exploited?
Attackers can exploit CWE-682 (Incorrect Calculation) to dos: crash, exit, or restart. This weakness is typically introduced during the Implementation phase of software development.
How do I prevent CWE-682?
Key mitigations include: Understand your programming language's underlying representation and how it interacts with numeric calculation. Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions,
What is the severity of CWE-682?
CWE-682 is classified as a Pillar-level weakness (Foundational abstraction). It has been observed in 3 real-world CVEs.