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CWE Common Weakness Enumeration

A community-developed list of SW & HW weaknesses that can become vulnerabilities
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Home > CWE List > CWE-125: Out-of-bounds Read (4.16)  
ID
CWE-125: Out-of-bounds Read
Weakness ID: 125
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: 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.
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+ Description
The product reads data past the end, or before the beginning, of the intended buffer. Diagram for CWE-125
+ Alternate Terms
OOB read:
Shorthand for "Out of bounds" read
+ 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.
Scope Impact Likelihood
Confidentiality

Technical Impact: Read Memory

An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality

Technical Impact: Bypass Protection Mechanism

Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability

Technical Impact: DoS: Crash, Exit, or Restart

An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely 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.
Other

Technical Impact: Varies by Context

The read operation could produce other undefined or unexpected results.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Phase: Architecture and Design

Strategy: Language Selection

Use a language that provides appropriate memory abstractions.
+ 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" (CWE-1000)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 119 Improper Restriction of Operations within the Bounds of a Memory Buffer
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 126 Buffer Over-read
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 127 Buffer Under-read
CanFollow 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. 822 Untrusted Pointer Dereference
CanFollow 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. 823 Use of Out-of-range Pointer Offset
CanFollow 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. 824 Access of Uninitialized Pointer
CanFollow 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. 825 Expired Pointer Dereference
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 "Software Development" (CWE-699)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1218 Memory Buffer Errors
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 "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 119 Improper Restriction of Operations within the Bounds of a Memory Buffer
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 "CISQ Quality Measures (2020)" (CWE-1305)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 119 Improper Restriction of Operations within the Bounds of a Memory Buffer
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 "CISQ Data Protection Measures" (CWE-1340)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 119 Improper Restriction of Operations within the Bounds of a Memory Buffer
+ 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
+ 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)

Technologies

Class: ICS/OT (Often Prevalent)

+ 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: C 
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: C 

...

// check that the array index is within the correct

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

...

+ Observed Examples
Reference Description
The reference implementation code for a Trusted Platform Module does not implement length checks on data, allowing for an attacker to read 2 bytes past the end of a buffer.
Out-of-bounds read in IP stack used in embedded systems, as exploited in the wild per CISA KEV.
Chain: "Heartbleed" bug receives an inconsistent length parameter (CWE-130) enabling an out-of-bounds read (CWE-126), returning memory that could include private cryptographic keys and other sensitive data.
HTML conversion package has a buffer under-read, allowing a crash
Chain: unexpected sign extension (CWE-194) leads to integer overflow (CWE-190), causing an out-of-bounds read (CWE-125)
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).
Chain: series of floating-point precision errors (CWE-1339) in a web browser rendering engine causes out-of-bounds read (CWE-125), giving access to cross-origin data
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
OS kernel trusts userland-supplied length value, allowing reading of sensitive information
+ Weakness Ordinalities
Ordinality Description
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
When an out-of-bounds read occurs, typically the product has already made a separate mistake, such as modifying an index or performing pointer arithmetic that produces an out-of-bounds address.
Primary
(where the weakness exists independent of other weaknesses)
+ Detection Methods

Fuzzing

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

Effectiveness: High

Automated Static Analysis

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.)

Effectiveness: High
+ 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. 970 SFP Secondary Cluster: Faulty Buffer Access
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. 1160 SEI CERT C Coding Standard - Guidelines 06. Arrays (ARR)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1161 SEI CERT C Coding Standard - Guidelines 07. Characters and Strings (STR)
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1200 Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1337 Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1350 Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1366 ICS Communications: Frail Security in Protocols
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1387 Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1399 Comprehensive Categorization: Memory Safety
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1425 Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1430 Weaknesses in the 2024 CWE Top 25 Most Dangerous Software Weaknesses
+ Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID may be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
+ Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Out-of-bounds Read
CERT C Secure Coding ARR30-C Imprecise Do not form or use out-of-bounds pointers or array subscripts
CERT C Secure Coding ARR38-C Imprecise Guarantee that library functions do not form invalid pointers
CERT C Secure Coding EXP39-C Imprecise Do not access a variable through a pointer of an incompatible type
CERT C Secure Coding STR31-C Imprecise Guarantee that storage for strings has sufficient space for character data and the null terminator
CERT C Secure Coding STR32-C CWE More Abstract Do not pass a non-null-terminated character sequence to a library function that expects a string
Software Fault Patterns SFP8 Faulty Buffer Access
+ References
[REF-1034] Raoul Strackx, Yves Younan, Pieter Philippaerts, Frank Piessens, Sven Lachmund and Thomas Walter. "Breaking the memory secrecy assumption". ACM. 2009-03-31. <https://dl.acm.org/doi/10.1145/1519144.1519145>. URL validated: 2023-04-07.
[REF-1035] Fermin J. Serna. "The info leak era on software exploitation". 2012-07-25. <https://media.blackhat.com/bh-us-12/Briefings/Serna/BH_US_12_Serna_Leak_Era_Slides.pdf>.
[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 Date Submitter Organization
2006-07-19
(CWE Draft 3, 2006-07-19) 		PLOVER
+ Contributions
Contribution Date Contributor Organization
2024-02-29
(CWE 4.15, 2024-07-16) 		Abhi Balakrishnan
Provided diagram to improve CWE usability
+ Modifications
Modification Date Modifier Organization
2008-09-08 CWE Content Team MITRE
updated Applicable_Platforms, Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2009-10-29 CWE Content Team MITRE
updated Description
2010-09-27 CWE Content Team MITRE
updated Relationships
2011-06-01 CWE Content Team MITRE
updated Common_Consequences
2012-05-11 CWE Content Team MITRE
updated Demonstrative_Examples, References, Relationships
2014-06-23 CWE Content Team MITRE
updated Related_Attack_Patterns
2014-07-30 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2015-12-07 CWE Content Team MITRE
updated Relationships
2017-11-08 CWE Content Team MITRE
updated Causal_Nature, Observed_Examples, Taxonomy_Mappings
2018-03-27 CWE Content Team MITRE
updated Description
2019-01-03 CWE Content Team MITRE
updated Relationships
2019-06-20 CWE Content Team MITRE
updated Description, Related_Attack_Patterns
2019-09-19 CWE Content Team MITRE
updated Common_Consequences, Observed_Examples, Potential_Mitigations, References, Relationships
2020-02-24 CWE Content Team MITRE
updated Potential_Mitigations, Relationships, Taxonomy_Mappings
2020-06-25 CWE Content Team MITRE
updated Observed_Examples, Potential_Mitigations
2020-08-20 CWE Content Team MITRE
updated Observed_Examples, Potential_Mitigations, Relationships
2020-12-10 CWE Content Team MITRE
updated Related_Attack_Patterns, Relationships
2021-07-20 CWE Content Team MITRE
updated Observed_Examples, Relationships
2022-04-28 CWE Content Team MITRE
updated Research_Gaps
2022-06-28 CWE Content Team MITRE
updated Observed_Examples, Relationships
2022-10-13 CWE Content Team MITRE
updated Applicable_Platforms, Relationships, Taxonomy_Mappings
2023-01-31 CWE Content Team MITRE
updated Description
2023-04-27 CWE Content Team MITRE
updated Detection_Factors, References, Relationships
2023-06-29 CWE Content Team MITRE
updated Mapping_Notes, Relationships
2023-10-26 CWE Content Team MITRE
updated Observed_Examples
2024-07-16
(CWE 4.15, 2024-07-16) 		CWE Content Team MITRE
updated Alternate_Terms, Common_Consequences, Description, Diagram, Weakness_Ordinalities
2024-11-19
(CWE 4.16, 2024-11-19) 		CWE Content Team MITRE
updated Observed_Examples, Relationships
Page Last Updated: November 19, 2024
 

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