CAPEC-46 Overflow Variables and Tags

This type of attack leverages the use of tags or variables from a formatted configuration data to cause buffer overflow. The adversary crafts a malicious HTML page or configuration file that includes oversized strings, thus causing an overflow.

1. [Explore] [Identify target application] The adversary identifies a target application or program to perform the buffer overflow on. Adversaries look for applications or programs that accept formatted files, such as configuration files, as input. 2. [Experiment] [Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer. 3. [Experiment] [Craft overflow content] The adversary crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary crafts the payload in such a way that the overwritten return address is replaced with one of the adversary's choosing. 4. [Exploit] [Overflow the buffer] The adversary will upload the crafted file to the application, causing a buffer overflow.

• The target program consumes user-controllable data in the form of tags or variables. • The target program does not perform sufficient boundary checking.

• [Low] An adversary can simply overflow a buffer by inserting a long string into an adversary-modifiable injection vector. The result can be a DoS. • [High] Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level.

• Availability: Unreliable Execution • Confidentiality, Integrity, Availability: Execute Unauthorized Commands • Confidentiality: Read Data • Integrity: Modify Data

• Use a language or compiler that performs automatic bounds checking. • Use an abstraction library to abstract away risky APIs. Not a complete solution. • Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. • Use OS-level preventative functionality. Not a complete solution. • Do not trust input data from user. Validate all user input.