CAPEC-10
Buffer Overflow via Environment Variables
HIGH
HIGH
Draft
2014-06-23 00:00 +00:00
2022-09-29 00:00 +00:00
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Description
This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the adversary finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
Informations
Execution Flow
1) Explore
[Identify target application] The adversary identifies a target application or program to perform the buffer overflow on. In this attack the adversary looks for an application that loads the content of an environment variable into a buffer.
2) Experiment
[Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer.
Technique
- Change the values of environment variables thought to be used by the application to contain excessive data. If the program is loading the value of the environment variable into a buffer, this could cause a crash and an attack vector will be found.
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.
Technique
- Create malicious shellcode that will execute when the program execution is returned to it.
- Use a NOP-sled in the overflow content to more easily "slide" into the malicious code. This is done so that the exact return address need not be correct, only in the range of all of the NOPs
4) Exploit
[Overflow the buffer] Using the injection vector, the adversary injects the crafted overflow content into the buffer.
Prerequisites
The application uses environment variables.An environment variable exposed to the user is vulnerable to a buffer overflow.
The vulnerable environment variable uses untrusted data.
Tainted data used in the environment variables is not properly validated. For instance boundary checking is not done before copying the input data to a buffer.
Skills Required
An attacker can simply overflow a buffer by inserting a long string into an attacker-modifiable injection vector. The result can be a DoS.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.
Mitigations
Do not expose environment variable to the user.Do not use untrusted data in your environment variables.
Use a language or compiler that performs automatic bounds checking
There are tools such as Sharefuzz [REF-2] which is an environment variable fuzzer for Unix that support loading a shared library. You can use Sharefuzz to determine if you are exposing an environment variable vulnerable to buffer overflow.
Related Weaknesses
| Weakness Name | |
|---|---|
| Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. |
|
| Authentication Bypass by Assumed-Immutable Data The authentication scheme or implementation uses key data elements that are assumed to be immutable, but can be controlled or modified by the attacker. |
|
| Incorrect Access of Indexable Resource ('Range Error') The product does not restrict or incorrectly restricts operations within the boundaries of a resource that is accessed using an index or pointer, such as memory or files. |
|
| Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data. |
|
| Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. |
|
| Improper Control of Resource Identifiers ('Resource Injection') The product receives input from an upstream component, but it does not restrict or incorrectly restricts the input before it is used as an identifier for a resource that may be outside the intended sphere of control. |
|
| Improper Input Validation The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. |
|
| Integer Overflow to Buffer Overflow The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow. |
|
| Compiler Optimization Removal or Modification of Security-critical Code The developer builds a security-critical protection mechanism into the software, but the compiler optimizes the program such that the mechanism is removed or modified. |
|
| Incorrect Comparison The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. |
References
REF-1
Exploiting Software: How to Break CodeG. Hoglund, G. McGraw.
REF-2
Sharefuzzhttp://sharefuzz.sourceforge.net
Submission
| Name | Organization | Date | Date Release |
|---|---|---|---|
| CAPEC Content Team | The MITRE Corporation |
Modifications
| Name | Organization | Date | Comment |
|---|---|---|---|
| CAPEC Content Team | The MITRE Corporation | Updated Related_Attack_Patterns | |
| CAPEC Content Team | The MITRE Corporation | Updated References | |
| CAPEC Content Team | The MITRE Corporation | Updated Mitigations | |
| CAPEC Content Team | The MITRE Corporation | Updated Taxonomy_Mappings | |
| CAPEC Content Team | The MITRE Corporation | Updated Execution_Flow, Extended_Description | |
| CAPEC Content Team | The MITRE Corporation | Updated Description | |
| CAPEC Content Team | The MITRE Corporation | Updated Example_Instances |
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