CAPEC-8: Buffer Overflow in an API Call
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.
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Overview
CAPEC-8 (Buffer Overflow in an API Call) is a detailed-level attack pattern catalogued by MITRE in the Common Attack Pattern Enumeration and Classification (CAPEC). It describes a recurring method attackers use to exploit software weaknesses.
How the attack works
The phases an attacker typically follows to carry out this attack.
- Step 1Explore
[Identify target application] The adversary, with knowledge of vulnerable libraries or shared code modules, identifies a target application or program that makes use of these.
- Step 2Experiment
[Find injection vector] The adversary attempts to use the API, and if they can they send a large amount of data to see if the buffer overflow attack really does work.
- Provide large input to a program or application and observe the behavior. If there is a crash, this means that a buffer overflow attack is possible.
- Step 3Experiment
[Craft overflow content] The adversary crafts the content to be injected based on their knowledge of the vulnerability and their desired outcome. 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 will craft a set of content that not only overflows the targeted buffer but does so in such a way that the overwritten return address is replaced with one of the adversaries' choosing which points to code injected by the adversary.
- 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
- Step 4Exploit
[Overflow the buffer] Using the API as the injection vector, the adversary injects the crafted overflow content into the buffer.
What the attacker needs
Prerequisites
- The target host exposes an API to the user.
- One or more API functions exposed by the target host has a buffer overflow vulnerability.
Skills required
- Low skill: An adversary can simply overflow a buffer by inserting a long string into an adversary-modifiable injection vector. The result can be a DoS.
- High skill: 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.
Consequences
What a successful CAPEC-8 attack can achieve.
Unreliable Execution
Affects: Availability
Execute Unauthorized Commands
Affects: Confidentiality, Integrity, Availability
Run Arbitrary Code
Read Data
Affects: Confidentiality
Modify Data
Affects: Integrity
How to mitigate it
Defenses that reduce the risk of CAPEC-8.
- Use a language or compiler that performs automatic bounds checking.
- Use secure functions not vulnerable to buffer overflow.
- If you have to use dangerous functions, make sure that you do boundary checking.
- 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.
Examples
Attack Example: Libc in FreeBSD A buffer overflow in the FreeBSD utility setlocale (found in the libc module) puts many programs at risk all at once.
Xtlib A buffer overflow in the Xt library of the X windowing system allows local users to execute commands with root privileges.
Frequently asked questions
Common questions about CAPEC-8.
- What is 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.
- How does a Buffer Overflow in an API Call attack work?
- It typically unfolds over 4 phases. It begins with: [Identify target application] The adversary, with knowledge of vulnerable libraries or shared code modules, identifies a target application or program that makes use of these.
- How do you prevent CAPEC-8?
- Use a language or compiler that performs automatic bounds checking.
- What weaknesses does CAPEC-8 target?
- CAPEC-8 exploits 8 CWE weaknesses, including 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).
- How severe is CAPEC-8?
- MITRE rates CAPEC-8 as High severity with high likelihood of attack.
References
Attack-pattern data is sourced from the MITRE CAPEC catalog (v3.9). Weakness associations link to the corresponding CWE entries on RadicalNotion.AI.
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