CWE - CWE-690: Unchecked Return Value to NULL Pointer Dereference (4.18)

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CWE Glossary Definition

CWE-690: Unchecked Return Value to NULL Pointer Dereference

Weakness ID: 690 (Structure: Chain) Chain - a Compound Element that is a sequence of two or more separate weaknesses that can be closely linked together within software. One weakness, X, can directly create the conditions that are necessary to cause another weakness, Y, to enter a vulnerable condition. When this happens, CWE refers to X as "primary" to Y, and Y is "resultant" from X. Chains can involve more than two weaknesses, and in some cases, they might have a tree-like structure.

Vulnerability Mapping: DISCOURAGED This CWE ID should not be used to map to real-world vulnerabilities

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Description

The product does not check for an error after calling a function that can return with a NULL pointer if the function fails, which leads to a resultant NULL pointer dereference.

Extended Description

While unchecked return value weaknesses are not limited to returns of NULL pointers (see the examples in CWE-252), functions often return NULL to indicate an error status. When this error condition is not checked, a NULL pointer dereference can occur.

Common Consequences

Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

Impact	Details
DoS: Crash, Exit, or Restart	Scope: Availability
Execute Unauthorized Code or Commands; Read Memory; Modify Memory	Scope: Integrity, Confidentiality, Availability In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.

Chain Components

Nature	Type	ID	Name
StartsWith	BaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value
FollowedBy	BaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	476	NULL Pointer Dereference

Relationships

Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

Relevant to the view "Research Concepts" (View-1000)

Nature	Type	ID	Name
ChildOf	Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	252	Unchecked Return Value

Modes Of Introduction

Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Phase	Note
Implementation	A typical occurrence of this weakness occurs when an application includes user-controlled input to a malloc() call. The related code might be correct with respect to preventing buffer overflows, but if a large value is provided, the malloc() will fail due to insufficient memory. This problem also frequently occurs when a parsing routine expects that certain elements will always be present. If malformed input is provided, the parser might return NULL. For example, strtok() can return NULL.

Phase

Note

Implementation

A typical occurrence of this weakness occurs when an application includes user-controlled input to a malloc() call. The related code might be correct with respect to preventing buffer overflows, but if a large value is provided, the malloc() will fail due to insufficient memory. This problem also frequently occurs when a parsing routine expects that certain elements will always be present. If malformed input is provided, the parser might return NULL. For example, strtok() can return NULL.

Applicable Platforms

Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Demonstrative Examples

Example 1

The code below makes a call to the getUserName() function but doesn't check the return value before dereferencing (which may cause a NullPointerException).

(bad code)

Example Language: Java

String username = getUserName();
if (username.equals(ADMIN_USER)) {

...

}

Example 2

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

(bad code)

Example Language: C

void host_lookup(char *user_supplied_addr){

struct hostent *hp;
in_addr_t *addr;
char hostname[64];
in_addr_t inet_addr(const char *cp);

/*routine that ensures user_supplied_addr is in the right format for conversion */

validate_addr_form(user_supplied_addr);
addr = inet_addr(user_supplied_addr);
hp = gethostbyaddr( addr, sizeof(struct in_addr), AF_INET);
strcpy(hostname, hp->h_name);

}

If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference (CWE-476) would then occur in the call to strcpy().

Note that this code is also vulnerable to a buffer overflow (CWE-119).

Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference	Description
CVE-2008-1052	Large Content-Length value leads to NULL pointer dereference when malloc fails.
CVE-2006-6227	Large message length field leads to NULL pointer dereference when malloc fails.
CVE-2006-2555	Parsing routine encounters NULL dereference when input is missing a colon separator.
CVE-2003-1054	URI parsing API sets argument to NULL when a parsing failure occurs, such as when the Referer header is missing a hostname, leading to NULL dereference.
CVE-2008-5183	chain: unchecked return value can lead to NULL dereference

Detection Methods

Method	Details
Black Box	This typically occurs in rarely-triggered error conditions, reducing the chances of detection during black box testing.
White Box	Code analysis can require knowledge of API behaviors for library functions that might return NULL, reducing the chances of detection when unknown libraries are used.

Memberships

Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.

Nature	Type	ID	Name
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	851	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 8 - Exceptional Behavior (ERR)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	876	CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1157	SEI CERT C Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1181	SEI CERT Perl Coding Standard - Guidelines 03. Expressions (EXP)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1399	Comprehensive Categorization: Memory Safety

Vulnerability Mapping Notes

Usage DISCOURAGED

(this CWE ID should not be used to map to real-world vulnerabilities)

Reason Other

Rationale

This CWE entry is a named chain, which combines multiple weaknesses.

Comments

Mapping to each separate weakness in the chain would be more precise.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CERT C Secure Coding	EXP34-C	CWE More Specific	Do not dereference null pointers
The CERT Oracle Secure Coding Standard for Java (2011)	ERR08-J	Do not catch NullPointerException or any of its ancestors
SEI CERT Perl Coding Standard	EXP32-PL	CWE More Specific	Do not ignore function return values

Content History

Submissions
Submission Date	Submitter	Organization
2008年04月11日 (CWE Draft 9, 2008年04月11日)	CWE Content Team	MITRE
2008年04月11日 (CWE Draft 9, 2008年04月11日)
Modifications
Modification Date	Modifier	Organization
2023年06月29日	CWE Content Team	MITRE
2023年06月29日	updated Mapping_Notes, Relationships
2023年04月27日	CWE Content Team	MITRE
2023年04月27日	updated Relationships
2021年03月15日	CWE Content Team	MITRE
2021年03月15日	updated Demonstrative_Examples, Relationships
2020年06月25日	CWE Content Team	MITRE
2020年06月25日	updated Common_Consequences
2019年01月03日	CWE Content Team	MITRE
2019年01月03日	updated Relationships, Taxonomy_Mappings
2017年11月08日	CWE Content Team	MITRE
2017年11月08日	updated Relationships, Relevant_Properties, Taxonomy_Mappings, Time_of_Introduction
2017年01月19日	CWE Content Team	MITRE
2017年01月19日	updated Relationships
2014年06月23日	CWE Content Team	MITRE
2014年06月23日	updated Modes_of_Introduction, Other_Notes
2011年09月13日	CWE Content Team	MITRE
2011年09月13日	updated Relationships, Taxonomy_Mappings
2011年06月01日	CWE Content Team	MITRE
2011年06月01日	updated Common_Consequences, Relationships, Taxonomy_Mappings
2010年09月27日	CWE Content Team	MITRE
2010年09月27日	updated Observed_Examples
2009年12月28日	CWE Content Team	MITRE
2009年12月28日	updated Demonstrative_Examples
2008年09月08日	CWE Content Team	MITRE
2008年09月08日	updated Applicable_Platforms, Description, Detection_Factors, Relationships, Other_Notes
2008年07月01日	Eric Dalci	Cigital
2008年07月01日	updated Time_of_Introduction
2008年07月01日	Sean Eidemiller	Cigital
2008年07月01日	added/updated demonstrative examples

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Page Last Updated: September 09, 2025

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