Cybersecurity Blog: Practical Buffer Overflow

Friday, April 4, 2014

Practical Buffer Overflow - Vulnerability Disclosure

Attackers generally use buffer overflows to corrupt the execution stack of a web application. By sending carefully crafted input to a web application, an attacker can cause the web application to execute arbitrary code, possibly taking over the machine. Attackers have managed to identify buffer overflows in a staggering array of products and components. Buffer overflow flaws can be present in both the web server and application server products that serve the static and dynamic portions of a site, or in the web application itself. Buffer overflows found in commonly-used server products are likely to become widely known and can pose a significant risk to users of these products. When web applications use libraries, such as a graphics library to generate images or a communications library to send e-mail, they open themselves to potential buffer overflow attacks.
Literature detailing buffer overflow attacks against commonly-used products is readily available, and newly discovered vulnerabilities are reported almost daily.

Buffer overflows can also be found in custom web application code, and may even be more likely, given the lack of scrutiny that web applications typically go through. Buffer overflow attacks against customized web applications can sometimes lead to interesting results. In some cases, we have discovered that sending large inputs can cause the web application or the back-end database to malfunction. It is possible to cause a denial of service attack against the web site, depending on the severity and specific nature of the flaw. Overly large inputs could cause the application to display a detailed error message, potentially leading to a successful attack on the system.

Vulnerability type – Buffer Overflow

Affected URL - http://download.nirmauni.ac.in/nrs/

Exploit Use – Copy whole exploit and input it into the authentication. Instead of giving authentication error, server breaks down and it discloses IIS coding settings.

Poc (Proof of Concept) –

Input exploit in authentication