CWE-456 变量未经初始化
Missing Initialization of a Variable
结构: Simple
Abstraction: Variant
状态: Draft
被利用可能性: unkown
基本描述
The software does not initialize critical variables, which causes the execution environment to use unexpected values.
相关缺陷
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cwe_Nature: ChildOf cwe_CWE_ID: 909 cwe_View_ID: 1000 cwe_Ordinal: Primary
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cwe_Nature: ChildOf cwe_CWE_ID: 909 cwe_View_ID: 699 cwe_Ordinal: Primary
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cwe_Nature: CanPrecede cwe_CWE_ID: 89 cwe_View_ID: 1000
-
cwe_Nature: CanPrecede cwe_CWE_ID: 120 cwe_View_ID: 1000
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cwe_Nature: CanPrecede cwe_CWE_ID: 98 cwe_View_ID: 1000
-
cwe_Nature: CanPrecede cwe_CWE_ID: 457 cwe_View_ID: 1000
-
cwe_Nature: CanPrecede cwe_CWE_ID: 457 cwe_View_ID: 699
适用平台
Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}
常见的影响
| 范围 | 影响 | 注释 |
|---|---|---|
| ['Integrity', 'Other'] | ['Unexpected State', 'Quality Degradation', 'Varies by Context'] | The uninitialized data may be invalid, causing logic errors within the program. In some cases, this could result in a security problem. |
可能的缓解方案
Implementation
策略:
Check that critical variables are initialized.
Testing
策略:
Use a static analysis tool to spot non-initialized variables.
示例代码
例
Here, an uninitialized field in a Java class is used in a seldom-called method, which would cause a NullPointerException to be thrown.
bad Java
public void someMethod() {
// Do something interesting.
...
// Throws NPE if user hasn't been properly initialized.
String username = user.getName();
}
例
This code first authenticates a user, then allows a delete command if the user is an administrator.
bad PHP
}
/.../
if ($isAdmin){
}
The $isAdmin variable is set to true if the user is an admin, but is uninitialized otherwise. If PHP's register_globals feature is enabled, an attacker can set uninitialized variables like $isAdmin to arbitrary values, in this case gaining administrator privileges by setting $isAdmin to true.
例
In the following Java code the BankManager class uses the user variable of the class User to allow authorized users to perform bank manager tasks. The user variable is initialized within the method setUser that retrieves the User from the User database. The user is then authenticated as unauthorized user through the method authenticateUser.
bad Java
// user allowed to perform bank manager tasks
private User user = null;
private boolean isUserAuthentic = false;
// constructor for BankManager class
public BankManager() {
}
// retrieve user from database of users
public User getUserFromUserDatabase(String username){
}
// set user variable using username
public void setUser(String username) {
}
// authenticate user
public boolean authenticateUser(String username, String password) {
}
return isUserAuthentic;
}
// methods for performing bank manager tasks
...
}
However, if the method setUser is not called before authenticateUser then the user variable will not have been initialized and will result in a NullPointerException. The code should verify that the user variable has been initialized before it is used, as in the following code.
good Java
// user allowed to perform bank manager tasks
private User user = null;
private boolean isUserAuthentic = false;
// constructor for BankManager class
public BankManager(String username) {
}
// retrieve user from database of users
public User getUserFromUserDatabase(String username) {...}
// authenticate user
public boolean authenticateUser(String username, String password) {
}
else {
}
}
return isUserAuthentic;
}
// methods for performing bank manager tasks
...
}
分析过的案例
| 标识 | 说明 | 链接 |
|---|---|---|
| CVE-2005-2978 | Product uses uninitialized variables for size and index, leading to resultant buffer overflow. | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2978 |
| CVE-2005-2109 | Internal variable in PHP application is not initialized, allowing external modification. | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2109 |
| CVE-2005-2193 | Array variable not initialized in PHP application, leading to resultant SQL injection. | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-2193 |
Notes
Relationship
This weakness is a major factor in a number of resultant weaknesses, especially in web applications that allow global variable initialization (such as PHP) with libraries that can be directly requested.
Research Gap
It is highly likely that a large number of resultant weaknesses have missing initialization as a primary factor, but researcher reports generally do not provide this level of detail.
分类映射
| 映射的分类名 | ImNode ID | Fit | Mapped Node Name |
|---|---|---|---|
| PLOVER | Missing Initialization | ||
| Software Fault Patterns | SFP1 | Glitch in computation | |
| CERT C Secure Coding | ERR30-C | CWE More Abstract | Set errno to zero before calling a library function known to set errno, and check errno only after the function returns a value indicating failure |
| SEI CERT Perl Coding Standard | DCL04-PL | Exact | Always initialize local variables |
| SEI CERT Perl Coding Standard | DCL33-PL | Imprecise | Declare identifiers before using them |
| OMG ASCSM | ASCSM-CWE-456 | ||
| OMG ASCRM | ASCRM-CWE-456 |
引用
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