CAPEC-52 Embedding NULL Bytes

An adversary embeds one or more null bytes in input to the target software. This attack relies on the usage of a null-valued byte as a string terminator in many environments. The goal is for certain components of the target software to stop processing the input when it encounters the null byte(s).

1. [Explore] [Survey the application for user-controllable inputs] Using a browser, an automated tool or by inspecting the application, an adversary records all entry points to the application. 2. [Experiment] [Probe entry points to locate vulnerabilities] The adversary uses the entry points gathered in the "Explore" phase as a target list and injects postfix null byte(s) to observe how the application handles them as input. The adversary is looking for areas where user input is placed in the middle of a string, and the null byte causes the application to stop processing the string at the end of the user input. 3. [Exploit] [Remove data after null byte(s)] After determined entry points that are vulnerable, the adversary places a null byte(s) such that they remove data after the null byte(s) in a way that is beneficial to them.

• The program does not properly handle postfix NULL terminators

• [Medium] Directory traversal • [High] Execution of arbitrary code

• Integrity: Modify Data • Confidentiality: Read Data • Confidentiality, Access Control, Authorization: Gain Privileges • Confidentiality, Integrity, Availability: Execute Unauthorized Commands

• Properly handle the NULL characters supplied as part of user input prior to doing anything with the data.