CWE Reference
CWE-122: Heap-based Buffer Overflow
Official CWE-122 CWE context with Glexia analysis, remediation guidance, related CVEs, and ATT&CK context.
Release 4.20weaknessDraft
Glexia's Take
CWE-122: Heap Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Availability: DoS: Crash, Exit, or Restart,DoS: Resource Consumption (CPU),DoS: Resource Consumption (Memory): Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
- Integrity,Confidentiality,Availability,Access Control: Execute Unauthorized Code or Commands,Bypass Protection Mechanism,Modify Memory: Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
- Integrity,Confidentiality,Availability,Access Control,Other: Execute Unauthorized Code or Commands,Bypass Protection Mechanism,Other: When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
Developer Pattern
CWE-122 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-122, 4.20.
Official CWE Definition
CWE-122: Heap-based Buffer Overflow
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, heap-based buffer overflows: The buffer is allocated heap memory with a fixed size, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow.
- This example applies an encoding procedure to an input string and stores it into a buffer. The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.
Remediation
- Pre-design: Use a language or compiler that performs automatic bounds checking.
- Architecture and Design: Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Operation,Build and Compilation: [object Object]
- Implementation: Implement and perform bounds checking on input.
- Implementation: Do not use dangerous functions such as gets. Look for their safe equivalent, which checks for the boundary.
- Operation: Use OS-level preventative functionality. This is not a complete solution, but it provides some defense in depth.
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 Dynamic Analysis: Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].
Mappings
Related CVEs, CWEs, and ATT&CK context
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.