Missing Release of Memory after Effective Lifetime

Description

This vulnerability occurs when a program allocates memory but fails to properly release it after it's no longer needed, causing a gradual accumulation of unused memory that can't be reclaimed by the system.

Extended Description

Memory leaks happen when developers allocate memory (e.g., using `malloc()`, `new`, or similar functions) but neglect to free or delete it once the relevant operation is complete. This often stems from complex control flows, error conditions, or long-running processes where tracking every allocation becomes difficult. Over time, especially in servers or persistent applications, these unreleased blocks accumulate, steadily draining available system memory. This resource exhaustion can lead to severe performance degradation, application instability, or complete crashes when the system runs out of memory. To prevent this, developers must ensure that every allocation has a corresponding, guaranteed release, using techniques like automatic resource management (e.g., smart pointers in C++, try-with-resources in Java), rigorous code reviews, and specialized leak detection tools during testing.

Common Consequences 2

Scope: Availability

Impact: DoS: Crash, Exit, or RestartDoS: InstabilityDoS: Resource Consumption (CPU)DoS: Resource Consumption (Memory)

Most memory leaks result in general product reliability problems, but if an attacker can intentionally trigger a memory leak, the attacker might be able to launch a denial of service attack (by crashing or hanging the program) or take advantage of other unexpected program behavior resulting from a low memory condition.

Scope: Other

Impact: Reduce Performance

Detection Methods 2

FuzzingHigh

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.

Automated Static AnalysisHigh

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.)

Potential Mitigations 3

Phase: Implementation

Strategy: Libraries or Frameworks

Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone. For example, glibc in Linux provides protection against free of invalid pointers. When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391]. To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

Phase: Architecture and Design

Use an abstraction library to abstract away risky APIs. Not a complete solution.

Phase: Architecture and DesignBuild and Compilation

The Boehm-Demers-Weiser Garbage Collector or valgrind can be used to detect leaks in code.

Demonstrative Examples 1

The following C function leaks a block of allocated memory if the call to read() does not return the expected number of bytes:

Code Example:Bad
C
c

Observed Examples 6

CVE-2005-3119Memory leak because function does not free() an element of a data structure.

CVE-2004-0427Memory leak when counter variable is not decremented.

CVE-2002-0574chain: reference count is not decremented, leading to memory leak in OS by sending ICMP packets.

CVE-2005-3181Kernel uses wrong function to release a data structure, preventing data from being properly tracked by other code.

CVE-2004-0222Memory leak via unknown manipulations as part of protocol test suite.

CVE-2001-0136Memory leak via a series of the same command.

References 4

The CLASP Application Security Process

Secure Software, Inc.

2005

https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf(2024-11-17)

ID: REF-18

How to Break Software Security

J. Whittaker and H. Thompson

Addison Wesley

2003

ID: REF-390

Transitioning to ARC Release Notes

iOS Developer Library

08-08-2013

https://developer.apple.com/library/archive/releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html(2023-04-07)

ID: REF-391

Automated Source Code Performance Efficiency Measure (ASCPEM)

Object Management Group (OMG)

01-2016

https://www.omg.org/spec/ASCPEM/(2023-04-07)

ID: REF-959

Likelihood of Exploit

Medium

Applicable Platforms

Languages:

C : UndeterminedC++ : Undetermined

Modes of Introduction

Implementation

Alternate Terms

Memory Leak

Functional Areas

Memory Management

Affected Resources

Memory

Related Weaknesses

ChildOf:

Missing Release of Resource after Effective Lifetime (CWE-772)

ChildOf:

Improper Resource Shutdown or Release (CWE-404)

ChildOf:

Improper Resource Shutdown or Release (CWE-404)

Taxonomy Mapping

PLOVER
7 Pernicious Kingdoms
CLASP
OWASP Top Ten 2004
CERT C Secure Coding
The CERT Oracle Secure Coding Standard for Java (2011)
Software Fault Patterns
OMG ASCPEM

Notes

RelationshipThis is often a resultant weakness due to improper handling of malformed data or early termination of sessions.

Terminology"memory leak" has sometimes been used to describe other kinds of issues, e.g. for information leaks in which the contents of memory are inadvertently leaked (CVE-2003-0400 is one such example of this terminology conflict).