Scope | Impact | Likelihood |
---|---|---|
Integrity Availability | DoS: Crash, Exit, or Restart Note: 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 Note: If the memory corrupted is data, rather than instructions, the system will continue to function with improper values. | |
Confidentiality Integrity | Modify Memory, Read Memory Note: 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 Note: 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 Note: 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. |
References | Description |
---|---|
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) |
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.
Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.
For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
When accessing a user-controlled array index, use a stringent range of values that are within the target array. Make sure that you do not allow negative values to be used. That is, verify the minimum as well as the maximum of the range of acceptable values.
Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
Be careful to avoid CWE-243 and other weaknesses related to jails.
This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.
Automated static analysis generally does not account for environmental considerations when reporting out-of-bounds memory operations. This can make it difficult for users to determine which warnings should be investigated first. For example, an analysis tool might report array index errors that originate from command line arguments in a program that is not expected to run with setuid or other special privileges.
CAPEC-ID | Attack Pattern Name |
---|---|
CAPEC-100 | Overflow Buffers Buffer Overflow attacks target improper or missing bounds checking on buffer operations, typically triggered by input injected by an adversary. As a consequence, an adversary is able to write past the boundaries of allocated buffer regions in memory, causing a program crash or potentially redirection of execution as per the adversaries' choice. |
Name | Organization | Date | Date release | Version |
---|---|---|---|---|
CLASP | Draft 3 |
Name | Organization | Date | Comment |
---|---|---|---|
Sean Eidemiller | Cigital | added/updated demonstrative examples | |
CWE Content Team | MITRE | updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities | |
CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Common_Consequences | |
CWE Content Team | MITRE | updated Description, Name, Relationships | |
CWE Content Team | MITRE | updated Applicable_Platforms, Common_Consequences, Observed_Examples, Other_Notes, Potential_Mitigations, Theoretical_Notes, Weakness_Ordinalities | |
CWE Content Team | MITRE | updated Applicable_Platforms, Demonstrative_Examples, Detection_Factors, Likelihood_of_Exploit, Potential_Mitigations, References, Related_Attack_Patterns, Relationships | |
CWE Content Team | MITRE | updated Related_Attack_Patterns | |
CWE Content Team | MITRE | updated Common_Consequences, Potential_Mitigations, References | |
CWE Content Team | MITRE | updated Potential_Mitigations, Relationship_Notes, Relationships | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Observed_Examples, Potential_Mitigations | |
CWE Content Team | MITRE | updated Common_Consequences, Demonstrative_Examples, Weakness_Ordinalities | |
CWE Content Team | MITRE | updated Common_Consequences | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Potential_Mitigations, References, Relationships | |
CWE Content Team | MITRE | updated Potential_Mitigations | |
CWE Content Team | MITRE | updated Potential_Mitigations, References | |
CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Causal_Nature, References, Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated References | |
CWE Content Team | MITRE | updated References, Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Potential_Mitigations | |
CWE Content Team | MITRE | updated Potential_Mitigations, Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Potential_Mitigations, Relationships, Type | |
CWE Content Team | MITRE | updated Potential_Mitigations, Relationships | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated References, Relationships | |
CWE Content Team | MITRE | updated References, Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Potential_Mitigations, References, Relationships | |
CWE Content Team | MITRE | updated Mapping_Notes |