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Improper Initialization

ID: 665Date: (C)2012-05-14   (M)2019-07-18
Type: weaknessStatus: DRAFT
Abstraction Type: Base


The software does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.

Extended Description

This can have security implications when the associated resource is expected to have certain properties or values, such as a variable that determines whether a user has been authenticated or not.

Likelihood of Exploit: Medium

Applicable Platforms
Language Class: Language-independent

Time Of Introduction

  • Implementation
  • Operation

Related Attack Patterns

Common Consequences

ScopeTechnical ImpactNotes
Read memory
Read 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.
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.
DoS: crash / exit / 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

Automated Dynamic Analysis
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.

Potential Mitigations

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.
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.
 Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage.
 Pay close attention to complex conditionals that affect initialization, since some conditions might not perform the initialization.
 Avoid race conditions (CWE-362) during initialization routines.
Build and Compilation
 Run or compile your software with settings that generate warnings about uninitialized variables or data.
 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.


Related CWETypeViewChain
CWE-665 ChildOf CWE-889 Category CWE-888  

Demonstrative Examples   (Details)

  1. 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.
  2. The following code intends to concatenate a string to a variable and print the string.
  3. The following code intends to limit certain operations to the administrator only. (Demonstrative Example Id DX-54)

Observed Examples

  1. CVE-2001-1471 : chain: an invalid value prevents a library file from being included, skipping initialization of key variables, leading to resultant eval injection.
  2. CVE-2008-3637 : Improper error checking in protection mechanism produces an uninitialized variable, allowing security bypass and code execution.
  3. CVE-2008-4197 : Use of uninitialized memory may allow code execution.
  4. CVE-2008-2934 : Free of an uninitialized pointer leads to crash and possible code execution.
  5. CVE-2007-3749 : OS kernel does not reset a port when starting a setuid program, allowing local users to access the port and gain privileges.
  6. CVE-2008-0063 : Product does not clear memory contents when generating an error message, leading to information leak.
  7. CVE-2008-0062 : Lack of initialization triggers NULL pointer dereference or double-free.
  8. CVE-2008-0081 : Uninitialized variable leads to code execution in popular desktop application.
  9. CVE-2008-3688 : chain: Uninitialized variable leads to infinite loop.
  10. CVE-2008-3475 : chain: Improper initialization leads to memory corruption.
  11. CVE-2008-5021 : Composite: race condition allows attacker to modify an object while it is still being initialized, causing software to access uninitialized memory.
  12. CVE-2005-1036 : Permission bitmap is not properly initialized, leading to resultant privilege elevation or DoS.
  13. CVE-2008-3597 : chain: game server can access player data structures before initialization has happened leading to NULL dereference
  14. CVE-2009-2692 : chain: uninitialized function pointers can be dereferenced allowing code execution
  15. CVE-2009-0949 : chain: improper initialization of memory can lead to NULL dereference
  16. CVE-2009-3620 : chain: some unprivileged ioctls do not verify that a structure has been initialized before invocation, leading to NULL dereference

For more examples, refer to CVE relations in the bottom box.

White Box Definitions

Black Box Definitions

Taxynomy Mappings

PLOVER  Incorrect initialization
CERT C Secure Coding ARR02-C
Explicitly specify array bounds, even if implicitly defined by an initializer
CERT C Secure Coding MEM09-C
Do not assume memory allocation routines initialize memory
CERT Java Secure Coding DCL00-J
Prevent class initialization cycles
CERT C++ Secure Coding ARR02-CPP
Explicitly specify array bounds, even if implicitly defined by an initializer
CERT C++ Secure Coding MEM09-CPP
Do not assume memory allocation routines initialize memory


  1. mercy .Exploiting Uninitialized Data. Published on Jan 2006.
  2. Microsoft Security Vulnerability Research & Defense .MS08-014 : The Case of the Uninitialized Stack Variable Vulnerability. 2008-03-11.
  3. Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 7, "Variable Initialization", Page 312.'. Published on 2006.
CVE    13

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