CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
Home > CWE List > CWE- Individual Dictionary Definition (3.1)  
ID

CWE-125: Out-of-bounds Read

Weakness ID: 125
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software reads data past the end, or before the beginning, of the intended buffer.
+ Extended Description
Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causinfg excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
+ Relationships

The table(s) below 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" (CWE-1000)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.119Improper Restriction of Operations within the Bounds of a Memory Buffer
ParentOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.126Buffer Over-read
ParentOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.127Buffer Under-read
CanFollowBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.822Untrusted Pointer Dereference
CanFollowBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.823Use of Out-of-range Pointer Offset
CanFollowBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.824Access of Uninitialized Pointer
CanFollowBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.825Expired Pointer Dereference
+ Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.119Improper Restriction of Operations within the Bounds of a Memory Buffer
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.119Improper Restriction of Operations within the Bounds of a Memory Buffer
ParentOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.126Buffer Over-read
ParentOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.127Buffer Under-read
+ Modes Of Introduction

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

PhaseNote
Implementation
+ Applicable Platforms
The listings below show 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)

+ Common Consequences

The table below 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.

ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Memory

+ Demonstrative Examples

Example 1

In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method

(bad code)
Example Language:
int getValueFromArray(int *array, int len, int index) {

int value;

// check that the array index is less than the maximum

// length of the array
if (index < len) {

// get the value at the specified index of the array
value = array[index];
}
// if array index is invalid then output error message

// and return value indicating error
else {
printf("Value is: %d\n", array[index]);
value = -1;
}

return value;
}

However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.

(good code)
Example Language:

...

// check that the array index is within the correct

// range of values for the array
if (index >= 0 && index < len) {

...
+ Observed Examples
ReferenceDescription
Chain: product does not handle when an input string is not NULL terminated (CWE-170), leading to buffer over-read (CWE-125) or heap-based buffer overflow (CWE-122).
out-of-bounds read due to improper length check
packet with large number of specified elements cause out-of-bounds read.
packet with large number of specified elements cause out-of-bounds read.
out-of-bounds read, resultant from integer underflow
large length value causes out-of-bounds read
malformed image causes out-of-bounds read
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Memberships
This 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.970SFP Secondary Cluster: Faulty Buffer Access
+ Notes

Research Gap

Under-studied and under-reported. Most issues are probably labeled as buffer overflows.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVEROut-of-bounds Read
Software Fault PatternsSFP8Faulty Buffer Access
CERT C Secure CodingARR30-CImpreciseDo not form or use out-of-bounds pointers or array subscripts
CERT C Secure CodingARR38-CImpreciseGuarantee that library functions do not form invalid pointers
CERT C Secure CodingEXP39-CImpreciseDo not access a variable through a pointer of an incompatible type
CERT C Secure CodingSTR31-CImpreciseGuarantee that storage for strings has sufficient space for character data and the null terminator
CERT C Secure CodingSTR32-CCWE More AbstractDo not pass a non-null-terminated character sequence to a library function that expects a string
+ References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.
+ Content History
Submissions
Submission DateSubmitterOrganization
PLOVER
Modifications
Modification DateModifierOrganization
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2009-10-29CWE Content TeamMITRE
updated Description
2010-09-27CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships
2014-06-23CWE Content TeamMITRE
updated Related_Attack_Patterns
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Causal_Nature, Observed_Examples, Taxonomy_Mappings
2018-03-27CWE Content TeamMITRE
updated Description

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Page Last Updated: March 29, 2018