10.7. Buffer Overflows
Buffer overflow occurs when an attempt is made to use a limited-length buffer to store a larger piece of data. Because of the lack of boundary checking, some amount of data will be written to memory locations immediately following the buffer. When an attacker manipulates program input, supplying specially crafted data payload, buffer overflows can be used to gain control of the application.
Buffer overflows affect C-based languages. Since most web applications are scripted (or written in Java, which is not vulnerable to buffer overflows), they are seldom affected by buffer overflows. Still, a typical web deployment can contain many components written in C:
Note that external systems such as databases, mail servers, directory servers and other servers are also often programmed in C. That the application itself is scripted is irrelevant. If data crosses system boundaries to reach the external system, an attacker could exploit a vulnerability.
A detailed explanation of how buffer overflows work falls outside the scope of this book. Consult the following resources to learn more: