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A heap overflow, heap overrun, or heap smashing is a type of buffer overflow that occurs in the heap data area. Heap overflows are exploitable in a different manner to that of stack-based overflows. Memory on the heap is dynamically allocated at runtime and typically contains program data. Exploitation is performed by corrupting this data in ...
Visualization of a software buffer overflow. Data is written into A, but is too large to fit within A, so it overflows into B.. In programming and information security, a buffer overflow or buffer overrun is an anomaly whereby a program writes data to a buffer beyond the buffer's allocated memory, overwriting adjacent memory locations.
Buffer overflow – out-of-bound writes can corrupt the content of adjacent objects, or internal data (like bookkeeping information for the heap) or return addresses. Buffer over-read – out-of-bound reads can reveal sensitive data or help attackers bypass address space layout randomization .
A heap spray can be used to introduce a large amount of order to compensate for this and increase the chances of successful exploitation. Heap sprays take advantage of the fact that on most architectures and operating systems, the start location of large heap allocations is predictable and consecutive allocations are roughly sequential.
Canaries or canary words or stack cookies are known values that are placed between a buffer and control data on the stack to monitor buffer overflows. When the buffer overflows, the first data to be corrupted will usually be the canary, and a failed verification of the canary data will therefore alert of an overflow, which can then be handled, for example, by invalidating the corrupted data.
A code sanitizer is a programming tool that detects bugs in the form of undefined or suspicious behavior by a compiler inserting instrumentation code at runtime. The class of tools was first introduced by Google's AddressSanitizer (or ASan) of 2012, which uses directly mapped shadow memory to detect memory corruption such as buffer overflows or accesses to a dangling pointer (use-after-free).
In a language with free pointers or non-checked array writes (such as in C), the mixing of control flow data which affects the execution of code (the return addresses or the saved frame pointers) and simple program data (parameters or return values) in a call stack is a security risk, and is possibly exploitable through stack buffer overflows ...
A "sawtooth" pattern of memory utilization may be an indicator of a memory leak within an application, particularly if the vertical drops coincide with reboots or restarts of that application. Care should be taken though because garbage collection points could also cause such a pattern and would show a healthy usage of the heap.