| Name |
Overflow Variables and Tags |
|
| Likelyhood of attack |
Typical severity |
| High |
High |
|
| Summary |
This type of attack leverages the use of tags or variables from a formatted configuration data to cause buffer overflow. The adversary crafts a malicious HTML page or configuration file that includes oversized strings, thus causing an overflow. |
| Prerequisites |
The target program consumes user-controllable data in the form of tags or variables. The target program does not perform sufficient boundary checking. |
| Execution Flow |
| Step |
Phase |
Description |
Techniques |
| 1 |
Explore |
[Identify target application] The adversary identifies a target application or program to perform the buffer overflow on. Adversaries look for applications or programs that accept formatted files, such as configuration files, as input. |
|
| 2 |
Experiment |
[Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer. |
- Knowing the type of file that an application takes as input, the adversary takes a normal input file and modifies a single variable or tag to contain a large amount of data. If there is a crash, this means that a buffer overflow attack is possible. The adversary will keep changing single variables or tags one by one until they see a change in behavior.
|
| 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. |
- 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] The adversary will upload the crafted file to the application, causing a buffer overflow. |
|
|
| Solutions | Use a language or compiler that performs automatic bounds checking. Use an abstraction library to abstract away risky APIs. Not a complete solution. Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. Use OS-level preventative functionality. Not a complete solution. Do not trust input data from user. Validate all user input. |
| Related Weaknesses |
|
CWE ID
|
Description
|
| CWE-20 |
Improper Input Validation |
| CWE-74 |
Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') |
| CWE-118 |
Incorrect Access of Indexable Resource ('Range Error') |
| CWE-119 |
Improper Restriction of Operations within the Bounds of a Memory Buffer |
| CWE-120 |
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') |
| CWE-680 |
Integer Overflow to Buffer Overflow |
| CWE-697 |
Incorrect Comparison |
| CWE-733 |
Compiler Optimization Removal or Modification of Security-critical Code |
|
| Related CAPECS |
|
CAPEC ID
|
Description
|
| CAPEC-8 |
This attack targets libraries or shared code modules which are vulnerable to buffer overflow attacks. An adversary who has knowledge of known vulnerable libraries or shared code can easily target software that makes use of these libraries. All clients that make use of the code library thus become vulnerable by association. This has a very broad effect on security across a system, usually affecting more than one software process. |
| CAPEC-10 |
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. |
| CAPEC-100 |
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. |
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