CAPEC 描述

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 資訊

執行流程

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.

技術

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.

技術

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.

前置條件

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.

所需技能

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.

緩解措施

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.

相關弱點

CWE-ID	弱點名稱
CWE-120	Buffer Copy without Checking Size of Input 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.
CWE-302	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.
CWE-118	Incorrect Access of Indexable Resource 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.
CWE-119	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.
CWE-74	Improper Neutralization of Special Elements in Output Used by a Downstream Component 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.
CWE-99	Improper Control of Resource Identifiers 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 control sphere.
CWE-20	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.
CWE-680	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.
CWE-733	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.
CWE-697	Incorrect Comparison The product compares two entities in a security-relevant context, but the comparison is incorrect.

參考資料

REF-1

Exploiting Software: How to Break Code
G. Hoglund, G. McGraw.

REF-2

Sharefuzz
http://sharefuzz.sourceforge.net

提交

名稱	機構	日期	發布日期
CAPEC Content Team	The MITRE Corporation	2014-06-23 +00:00

修改記錄

名稱	機構	日期	備註
CAPEC Content Team	The MITRE Corporation	2017-01-09 +00:00	Updated Related_Attack_Patterns
CAPEC Content Team	The MITRE Corporation	2018-07-31 +00:00	Updated References
CAPEC Content Team	The MITRE Corporation	2020-07-30 +00:00	Updated Mitigations
CAPEC Content Team	The MITRE Corporation	2020-12-17 +00:00	Updated Taxonomy_Mappings
CAPEC Content Team	The MITRE Corporation	2021-10-21 +00:00	Updated Execution_Flow, Extended_Description
CAPEC Content Team	The MITRE Corporation	2022-02-22 +00:00	Updated Description
CAPEC Content Team	The MITRE Corporation	2022-09-29 +00:00	Updated Example_Instances

CAPEC-10 詳細資料

CAPEC-10