Description

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.

Modes of Introduction:

– Implementation

 

Likelihood of Exploit: High

 

Related Weaknesses

CWE-1285
CWE-20
CWE-119
CWE-823
CWE-789

 

Consequences

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

Use of an index that is outside the bounds of an array will very likely result in the corruption of relevant memory and perhaps instructions, leading to a crash, if the values are outside of the valid memory area.

Integrity: Modify Memory

If the memory corrupted is data, rather than instructions, the system will continue to function with improper values.

Confidentiality, Integrity: Modify Memory, Read Memory

Use of an index that is outside the bounds of an array can also trigger out-of-bounds read or write operations, or operations on the wrong objects; i.e., “buffer overflows” are not always the result. This may result in the exposure or modification of sensitive data.

Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands

If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow and possibly without the use of large inputs if a precise index can be controlled.

Integrity, Availability, Confidentiality: DoS: Crash, Exit, or Restart, Execute Unauthorized Code or Commands, Read Memory, Modify Memory

A single fault could allow either an overflow (CWE-788) or underflow (CWE-786) of the array index. What happens next will depend on the type of operation being performed out of bounds, but can expose sensitive information, cause a system crash, or possibly lead to arbitrary code execution.

 

Potential Mitigations

Phase: Architecture and Design

Description: 

Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).

Phase: Architecture and Design

Description: 

Phase: Requirements

Description: 

Phase: Operation

Effectiveness: Defense in Depth

Description: 

This is not a complete solution. However, it forces the attacker to guess an unknown value that changes every program execution. In addition, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Operation

Effectiveness: Defense in Depth

Description: 

Use a CPU and operating system that offers Data Execution Protection (NX) or its equivalent [REF-60] [REF-61].

This is not a complete solution, since buffer overflows could be used to overwrite nearby variables to modify the software’s state in dangerous ways. In addition, it cannot be used in cases in which self-modifying code is required. Finally, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Implementation

Description: 

Phase: Implementation

Description: 

Be especially careful to validate all input when invoking code that crosses language boundaries, such as from an interpreted language to native code. This could create an unexpected interaction between the language boundaries. Ensure that you are not violating any of the expectations of the language with which you are interfacing. For example, even though Java may not be susceptible to buffer overflows, providing a large argument in a call to native code might trigger an overflow.

Phase: Architecture and Design, Operation

Description: 

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phase: Architecture and Design, Operation

Effectiveness: Limited

Description: 

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

CVE References

• CVE-2005-0369
  • large ID in packet used as array index

• CVE-2001-1009
  • negative array index as argument to POP LIST command

• CVE-2003-0721
  • Integer signedness error leads to negative array index

• CVE-2004-1189
  • product does not properly track a count and a maximum number, which can lead to resultant array index overflow.

• CVE-2007-5756
  • Chain: device driver for packet-capturing software allows access to an unintended IOCTL with resultant array index error.

• CVE-2005-2456
  • Chain: array index error (CWE-129) leads to deadlock (CWE-833)