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Improper Initialization

Draft Class
Structure: Simple
Description

This vulnerability occurs when software fails to properly set up a resource before use, or provides incorrect starting values, leaving it in an unpredictable and potentially dangerous state.

Extended Description

Improper initialization happens when a developer doesn't assign a correct starting value to a variable, object, or system resource. Without this crucial setup step, the resource contains whatever random data was already in memory (often called "garbage values"), leading to erratic and unpredictable behavior when the program tries to use it. From a security perspective, this flaw is critical because many security decisions rely on checking the state of a variable. For example, an authentication flag that isn't explicitly set to "false" might accidentally retain a "true" value from a previous operation, granting unauthorized access. Always explicitly initialize all variables and resources to a known, safe state to eliminate this risk.
Common Consequences 3
Scope: Confidentiality

Impact: Read MemoryRead Application Data

When reusing a resource such as memory or a program variable, the original contents of that resource may not be cleared before it is sent to an untrusted party.

Scope: Access Control

Impact: Bypass Protection Mechanism

If security-critical decisions rely on a variable having a "0" or equivalent value, and the programming language performs this initialization on behalf of the programmer, then a bypass of security may occur.

Scope: Availability

Impact: DoS: Crash, Exit, or Restart

The uninitialized data may contain values that cause program flow to change in ways that the programmer did not intend. For example, if an uninitialized variable is used as an array index in C, then its previous contents may produce an index that is outside the range of the array, possibly causing a crash or an exit in other environments.
Detection Methods 3
Automated Dynamic AnalysisModerate
This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results. Initialization problems may be detected with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
Manual Dynamic Analysis
Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still indicate unexpected conditions that were not handled by the application itself.
Automated Static AnalysisHigh
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Potential Mitigations 7
Phase: Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, in Java, if the programmer does not explicitly initialize a variable, then the code could produce a compile-time error (if the variable is local) or automatically initialize the variable to the default value for the variable's type. In Perl, if explicit initialization is not performed, then a default value of undef is assigned, which is interpreted as 0, false, or an equivalent value depending on the context in which the variable is accessed.
Phase: Architecture and Design
Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.
Phase: Implementation
Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage.
Phase: Implementation
Pay close attention to complex conditionals that affect initialization, since some conditions might not perform the initialization.
Phase: Implementation
Avoid race conditions (Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')) during initialization routines.
Phase: Build and Compilation
Run or compile your product with settings that generate warnings about uninitialized variables or data.
Phase: Testing
Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.
Demonstrative Examples 3

ID : DX-105

Here, a boolean initiailized field is consulted to ensure that initialization tasks are only completed once. However, the field is mistakenly set to true during static initialization, so the initialization code is never reached.

Code Example:

Bad
Java
java

// perform initialization tasks* ...

java

ID : DX-54

The following code intends to limit certain operations to the administrator only.

Code Example:

Bad
Perl
perl

do stuff*

perl
If the application is unable to extract the state information - say, due to a database timeout - then the $uid variable will not be explicitly set by the programmer. This will cause $uid to be regarded as equivalent to "0" in the conditional, allowing the original user to perform administrator actions. Even if the attacker cannot directly influence the state data, unexpected errors could cause incorrect privileges to be assigned to a user just by accident.
ID : DX-106
The following code intends to concatenate a string to a variable and print the string.
Code Example:
Bad
C
c
This might seem innocent enough, but str was not initialized, so it contains random memory. As a result, str[0] might not contain the null terminator, so the copy might start at an offset other than 0. The consequences can vary, depending on the underlying memory.
If a null terminator is found before str[8], then some bytes of random garbage will be printed before the "hello world" string. The memory might contain sensitive information from previous uses, such as a password (which might occur as a result of Compiler Removal of Code to Clear Buffers or Improper Clearing of Heap Memory Before Release ('Heap Inspection')). In this example, it might not be a big deal, but consider what could happen if large amounts of memory are printed out before the null terminator is found.
If a null terminator isn't found before str[8], then a buffer overflow could occur, since strcat will first look for the null terminator, then copy 12 bytes starting with that location. Alternately, a buffer over-read might occur (Buffer Over-read) if a null terminator isn't found before the end of the memory segment is reached, leading to a segmentation fault and crash.
  
Observed Examples 16
CVE-2001-1471chain: an invalid value prevents a library file from being included, skipping initialization of key variables, leading to resultant eval injection.
CVE-2008-3637Improper error checking in protection mechanism produces an uninitialized variable, allowing security bypass and code execution.
CVE-2008-4197Use of uninitialized memory may allow code execution.
CVE-2008-2934Free of an uninitialized pointer leads to crash and possible code execution.
CVE-2007-3749OS kernel does not reset a port when starting a setuid program, allowing local users to access the port and gain privileges.
CVE-2008-0063Product does not clear memory contents when generating an error message, leading to information leak.
CVE-2008-0062Lack of initialization triggers NULL pointer dereference or double-free.
CVE-2008-0081Uninitialized variable leads to code execution in popular desktop application.
CVE-2008-3688chain: Uninitialized variable leads to infinite loop.
CVE-2008-3475chain: Improper initialization leads to memory corruption.
CVE-2008-5021Composite: race condition allows attacker to modify an object while it is still being initialized, causing software to access uninitialized memory.
CVE-2005-1036Chain: Bypass of access restrictions due to improper authorization (Missing Authorization) of a user results from an improperly initialized (Missing Initialization of Resource) I/O permission bitmap
CVE-2008-3597chain: game server can access player data structures before initialization has happened leading to NULL dereference
CVE-2009-2692chain: uninitialized function pointers can be dereferenced allowing code execution
CVE-2009-0949chain: improper initialization of memory can lead to NULL dereference
CVE-2009-3620chain: some unprivileged ioctls do not verify that a structure has been initialized before invocation, leading to NULL dereference
  
References 3
Exploiting Uninitialized Data
mercy
01-2006
https://web.archive.org/web/20070403193636/http://www.felinemenace.org/~mercy/papers/UBehavior/UBehavior.zip(2025-07-24)
ID: REF-436
MS08-014 : The Case of the Uninitialized Stack Variable Vulnerability
Microsoft Security Vulnerability Research & Defense
11-03-2008
https://msrc.microsoft.com/blog/2008/03/ms08-014-the-case-of-the-uninitialized-stack-variable-vulnerability/(2023-04-07)
ID: REF-437
The Art of Software Security Assessment
Mark Dowd, John McDonald, and Justin Schuh
Addison Wesley
2006
ID: REF-62
 
  
  
 
 
Likelihood of Exploit 
 
 
 
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Applicable Platforms 
 
 
 
 
 
Languages:
 
 
 Not Language-Specific : Undetermined 
  
  
 
 
 
  
 
 
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Related Attack Patterns 
        
 
 
Related Weaknesses 
 
 
 
 
  ChildOf:
 Improper Control of a Resource Through its Lifetime (CWE-664) 
 
 
 
 
Taxonomy Mapping 
  • PLOVER
  • CERT C Secure Coding
  • The CERT Oracle Secure Coding Standard for Java (2011)
  • Software Fault Patterns