123 (Weakness Base)

High

Resultant (Weakness is typically related to the presence of some other weaknesses)

Explicit (This is an explicit weakness resulting from behavior of the developer)

Access control (memory and instruction processing): Clearly, write-what-where conditions can be used to write data to areas of memory outside the scope of a policy. Also, they almost invariably can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.

Availability: Many memory accesses can lead to program termination, such as when writing to addresses that are invalid for the current process.

Other: When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

Pre-design: Use a language that provides appropriate memory abstractions.

Design: Integrate technologies that try to prevent the consequences of this problem.

Implementation: Take note of mitigations provided for other flaws in this taxonomy that lead to write-what-where conditions.

Operational: Use OS-level preventative functionality integrated after the fact. Not a complete solution.

When the attacker has the ability to write arbitrary data to an arbitrary location in memory, the consequences are often arbitrary code execution. If the attacker can overwrite a pointer's worth of memory (usually 32 or 64 bits), he can redirect a function pointer to his own malicious code. Even when the attacker can only modify a single byte using a write-what-where problem, arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data -- such as a flag indicating whether the user is an administrator.

CLASP - Write-what-where condition

C

C++