Common Weakness Enumeration

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CWE-824: Access of Uninitialized Pointer

Weakness ID: 824
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The program accesses or uses a pointer that has not been initialized.

Extended Description

If the pointer contains an uninitialized value, then the value might not point to a valid memory location. This could cause the program to read from or write to unexpected memory locations, leading to a denial of service. If the uninitialized pointer is used as a function call, then arbitrary functions could be invoked. If an attacker can influence the portion of uninitialized memory that is contained in the pointer, this weakness could be leveraged to execute code or perform other attacks.

Depending on memory layout, associated memory management behaviors, and program operation, the attacker might be able to influence the contents of the uninitialized pointer, thus gaining more fine-grained control of the memory location to be accessed.

+ Terminology Notes

Many weaknesses related to pointer dereferences fall under the general term of "memory corruption" or "memory safety." As of September 2010, there is no commonly-used terminology that covers the lower-level variants.

+ Common Consequences

Technical Impact: Read memory

If the uninitialized pointer is used in a read operation, an attacker might be able to read sensitive portions of memory.


Technical Impact: DoS: crash / exit / restart

If the uninitialized pointer references a memory location that is not accessible to the program, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.


Technical Impact: Execute unauthorized code or commands

If the uninitialized pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.

+ Observed Examples
chain: unchecked return value (CWE-252) leads to free of invalid, uninitialized pointer (CWE-824).
Pointer in structure is not initialized, leading to NULL pointer dereference (CWE-476) and system crash.
Free of an uninitialized pointer.
Improper handling of invalid signatures leads to free of invalid pointer.
Invalid encoding triggers free of uninitialized pointer.
Crafted PNG image leads to free of uninitialized pointer.
Crafted GIF image leads to free of uninitialized pointer.
Access of uninitialized pointer might lead to code execution.
Step-based manipulation: invocation of debugging function before the primary initialization function leads to access of an uninitialized pointer and code execution.
Unchecked return values can lead to a write to an uninitialized pointer.
zero-length input leads to free of uninitialized pointer.
Crafted font leads to uninitialized function pointer.
Uninitialized function pointer in freed memory is invoked
LDAP server mishandles malformed BER queries, leading to free of uninitialized memory
Firewall can crash with certain ICMP packets that trigger access of an uninitialized pointer.
LDAP server does not initialize members of structs, which leads to free of uninitialized pointer if an LDAP request fails.
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class119Improper Restriction of Operations within the Bounds of a Memory Buffer
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory465Pointer Issues
Development Concepts699
CanPrecedeWeakness BaseWeakness Base125Out-of-bounds Read
Research Concepts1000
CanPrecedeWeakness BaseWeakness Base787Out-of-bounds Write
Research Concepts1000
+ Research Gaps

Under-studied and probably under-reported as of September 2010. This weakness has been reported in high-visibility software, but applied vulnerability researchers have only been investigating it since approximately 2008, and there are only a few public reports. Few reports identify weaknesses at such a low level, which makes it more difficult to find and study real-world code examples.

+ References
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Variable Initialization", Page 312.. 1st Edition. Addison Wesley. 2006.
+ Maintenance Notes

There are close relationships between incorrect pointer dereferences and other weaknesses related to buffer operations. There may not be sufficient community agreement regarding these relationships. Further study is needed to determine when these relationships are chains, composites, perspective/layering, or other types of relationships. As of September 2010, most of the relationships are being captured as chains.

+ Content History
Submission DateSubmitterOrganizationSource
2010-09-22MITREInternal CWE Team
Modification DateModifierOrganizationSource
2012-05-11CWE Content TeamMITREInternal
updated References
2015-12-07CWE Content TeamMITREInternal
updated Relationships

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Page Last Updated: January 18, 2017