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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. Buffers are areas of memory set aside to hold data, often while moving it from one section of a program to another, or between programs.
Memory errors were first considered in the context of resource management (computing) and time-sharing systems, in an effort to avoid problems such as fork bombs. [4] Developments were mostly theoretical until the Morris worm , which exploited a buffer overflow in fingerd . [ 5 ]
In computer science, an array is a data structure consisting of a collection of elements (values or variables), of same memory size, each identified by at least one array index or key. An array is stored such that the position of each element can be computed from its index tuple by a mathematical formula. [1][2][3] The simplest type of data ...
To illustrate, suppose a is the memory address of the first element of an array, and i is the index of the desired element. To compute the address of the desired element, if the index numbers count from 1, the desired address is computed by this expression: + (), where s is the size of each element. In contrast, if the index numbers count from ...
Lookup table. In computer science, a lookup table (LUT) is an array that replaces runtime computation with a simpler array indexing operation, in a process termed as direct addressing. The savings in processing time can be significant, because retrieving a value from memory is often faster than carrying out an "expensive" computation or input ...
Stack buffer overflow. In software, a stack buffer overflow or stack buffer overrun occurs when a program writes to a memory address on the program's call stack outside of the intended data structure, which is usually a fixed-length buffer. [1][2] Stack buffer overflow bugs are caused when a program writes more data to a buffer located on the ...
Uninitialized variables are powerful bugs since they can be exploited to leak arbitrary memory or to achieve arbitrary memory overwrite or to gain code execution, depending on the case. When exploiting a software which utilizes address space layout randomization (ASLR), it is often required to know the base address of the software in memory.
A memory address a is said to be n-byte aligned when a is a multiple of n (where n is a power of 2). In this context, a byte is the smallest unit of memory access, i.e. each memory address specifies a different byte. An n-byte aligned address would have a minimum of log 2 (n) least-significant zeros when expressed in binary.