CWE-401: Missing Release of Memory after Effective Lifetime
Weakness ID: 401
Vulnerability Mapping:ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction:
VariantVariant - 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.
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Description
The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.
Extended Description
This is often triggered by improper handling of malformed data or unexpectedly interrupted sessions. In some languages, developers are responsible for tracking memory allocation and releasing the memory. If there are no more pointers or references to the memory, then it can no longer be tracked and identified for release.
Alternate Terms
Memory Leak
Common Consequences
This 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.
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.
Other
Technical Impact: Reduce Performance
Potential Mitigations
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.
Phases: Architecture and Design; Build and Compilation
The Boehm-Demers-Weiser Garbage Collector or valgrind can be used to detect leaks in code.
Note:
This is not a complete solution as it is not 100% effective.
Relationships
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
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.
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.
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 - 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.
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 - 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.
The 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
Memory leaks have two common and sometimes overlapping causes:
Error conditions and other exceptional circumstances
Confusion over which part of the program is responsible for freeing the memory
Applicable Platforms
This 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)
Likelihood Of Exploit
Medium
Demonstrative Examples
Example 1
The following C function leaks a block of allocated memory if the call to read() does not return the expected number of bytes:
(bad code)
Example Language: C
char* getBlock(int fd) {
char* buf = (char*) malloc(BLOCK_SIZE); if (!buf) {
(where the weakness is typically related to the presence of some 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
Functional Areas
Memory Management
Affected Resources
Memory
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.
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
(this CWE ID may be used to map to real-world vulnerabilities)
Reason:
Acceptable-Use
Rationale:
This CWE entry is at the Variant 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.
Notes
Relationship
This 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).
Taxonomy
Mappings
Mapped Taxonomy Name
Node ID
Fit
Mapped Node Name
PLOVER
Memory leak
7 Pernicious Kingdoms
Memory Leak
CLASP
Failure to deallocate data
OWASP Top Ten 2004
A9
CWE More Specific
Denial of Service
CERT C Secure Coding
MEM31-C
Exact
Free dynamically allocated memory when no longer needed
The CERT Oracle Secure Coding Standard for Java (2011)
Description
This 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.
