Description

Any condition where the attacker has the ability to write an arbitrary value to an arbitrary location, often as the result of a buffer overflow.

Modes of Introduction:

– Implementation

Likelihood of Exploit: High

Related Weaknesses

CWE-787
CWE-119
CWE-119

Consequences

Integrity, Confidentiality, Availability, Access Control: Modify Memory, Execute Unauthorized Code or Commands, Gain Privileges or Assume Identity, DoS: Crash, Exit, or Restart, Bypass Protection Mechanism

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. If the attacker can overwrite a pointer’s worth of memory (usually 32 or 64 bits), they can redirect a function pointer to their own malicious code. Even when the attacker can only modify a single byte 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.

Integrity, Availability: DoS: Crash, Exit, or Restart, Modify Memory

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

Access Control, Other: Bypass Protection Mechanism, Other

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

Potential Mitigations

Phase: Architecture and Design

Description: 

Use a language that provides appropriate memory abstractions.

Phase: Operation

Description: 

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

CVE References