What CVEs are caused by CWE-126?

481 recorded CVEs are attributed to CWE-126, including CVE-2024-49839, CVE-2023-36397, CVE-2023-22385.

What are the consequences of CWE-126?

Exploiting CWE-126 can lead to: Read Memory, Bypass Protection Mechanism, DoS: Crash, Exit, or Restart.

Is CWE-126 actively exploited?

481 recorded CVEs are caused by CWE-126; none are currently in CISA's KEV catalog of actively exploited flaws.

Variant weakness

Draft

CWE-126: Buffer Over-read

The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.

Last updated May 1, 2026

481

Recorded CVEs

With this primary weakness

KEVs

In the CISA KEV catalog

Not rated

Likelihood of exploit

Per MITRE

Variant

Abstraction

MITRE classification

Overview

CWE-126 (Buffer Over-read) is a variant-level software weakness catalogued by MITRE in the Common Weakness Enumeration (CWE). It describes a recurring type of mistake that can lead to exploitable security vulnerabilities.

Real-world CVEs

481 recorded CVEs are caused by CWE-126 (Buffer Over-read). The highest-severity and most recent are shown first. 93 new CWE-126 CVEs have been recorded so far in 2026 (115 in 2025).

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Common consequences

What can happen when CWE-126 is exploited.

Read Memory

Affects: Confidentiality

Bypass Protection Mechanism

Affects: Confidentiality

By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service.

DoS: Crash, Exit, or Restart

Affects: Availability, Integrity

An attacker might be able to cause a crash or other denial of service by causing the product to read a memory location that is not allowed (such as a segmentation fault), or to cause other conditions in which the read operation returns more data than is expected.

How it happens

When it is introduced

Typically introduced during these phases of the software lifecycle.

Implementation

Applies to

Languages

Memory-Unsafe

C++

How to detect it

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

Automated Dynamic Analysis

Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

Effectiveness: Moderate

Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.

Vulnerable example

int processMessageFromSocket(int socket) {

However, the message length variable (msgLength) from the structure is used as the condition for ending the for loop without validating that msgLength accurately reflects the actual length of the message body (CWE-606). If msgLength indicates a length that is longer than the size of a message body (CWE-130), then this can result in a buffer over-read by reading past the end of the buffer (CWE-126).

The following C/C++ example demonstrates a buffer over-read due to a missing NULL terminator. The main method of a pattern matching utility that looks for a specific pattern within a specific file uses the string strncopy() method to copy the command line user input file name and pattern to the Filename and Pattern character arrays respectively.

Vulnerable example

int main(int argc, char **argv)

Illustrative examples

Real CVEs that MITRE cites as examples of this weakness.

CVE-2014-0160
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.
CVE-2022-1733 — Text editor has out-of-bounds read past end of line while indenting C code
CVE-2009-2523 — Chain: product does not handle when an input string is not NULL terminated, leading to buffer over-read or heap-based buffer overflow.

Terminology & mappings

Mapped taxonomies

PLOVER: Buffer over-read
Software Fault Patterns: Faulty Buffer Access (SFP8)

Frequently asked questions

Common questions about CWE-126.

What is CWE-126?: The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
What CVEs are caused by CWE-126?: 481 recorded CVEs are attributed to CWE-126, including CVE-2024-49839, CVE-2023-36397, CVE-2023-22385.
How is CWE-126 detected?: 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.)
What are the consequences of CWE-126?: Exploiting CWE-126 can lead to: Read Memory, Bypass Protection Mechanism, DoS: Crash, Exit, or Restart.
Is CWE-126 actively exploited?: 481 recorded CVEs are caused by CWE-126; none are currently in CISA's KEV catalog of actively exploited flaws.

References

Weakness data is sourced from the MITRE CWE catalog (v4.20). CVE associations are aggregated and kept current by RadicalNotion.AI.

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