CWE - CWE-502: Deserialization of Untrusted Data (4.19.1)

CWE -

CWE-502: Deserialization of Untrusted Data (4.19.1)
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CWE-502: Deserialization of Untrusted Data (4.19.1)
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CWE Glossary Definition
CWE-502: Deserialization of Untrusted Data
Weakness ID: 502
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 deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
Alternate Terms
Marshaling, Unmarshaling
Marshaling and unmarshaling are effectively synonyms for serialization and deserialization, respectively.
Pickling, Unpickling
In Python, the "pickle" functionality is used to perform serialization and deserialization.
PHP Object Injection
Some PHP application researchers use this term when attacking unsafe use of the unserialize() function; but it is also used for
CWE-915
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.
Impact
Details
Modify Application Data; Unexpected State
Scope: Integrity
Attackers can modify unexpected objects or data that was assumed to be safe from modification. Deserialized data or code could be modified without using the provided accessor functions, or unexpected functions could be invoked.
DoS: Resource Consumption (CPU)
Scope: Availability
If a function is making an assumption on when to terminate, based on a sentry in a string, it could easily never terminate.
Varies by Context
Scope: Other
The consequences can vary widely, because it depends on which objects or methods are being deserialized, and how they are used. Making an assumption that the code in the deserialized object is valid is dangerous and can enable exploitation. One example is attackers using gadget chains to perform unauthorized actions, such as generating a shell.
Potential Mitigations
Phase(s)
Mitigation
Architecture and Design; Implementation
If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
Implementation
When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
Implementation
Explicitly define a final object() to prevent deserialization.
Architecture and Design; Implementation
Make fields transient to protect them from deserialization.
An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.
Implementation
Avoid having unnecessary types or gadgets (a sequence of instances and method invocations that can self-execute during the deserialization process, often found in libraries) available that can be leveraged for malicious ends. This limits the potential for unintended or unauthorized types and gadgets to be leveraged by the attacker. Add only acceptable classes to an allowlist. Note: new gadgets are constantly being discovered, so this alone is not a sufficient mitigation.
Architecture and Design; Implementation
Employ cryptography of the data or code for protection. However, it's important to note that it would still be client-side security. This is risky because if the client is compromised then the security implemented on the client (the cryptography) can be bypassed.
Operation
Strategy:
Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [
REF-1481
].
Effectiveness: Moderate
Note:
An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.
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" (View-1000)
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.
913
Improper Control of Dynamically-Managed Code Resources
PeerOf
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.
915
Improperly Controlled Modification of Dynamically-Determined Object Attributes
Relevant to the view "Software Development" (View-699)
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
399
Resource Management Errors
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-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.
913
Improper Control of Dynamically-Managed Code Resources
Relevant to the view "Architectural Concepts" (View-1008)
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1019
Validate Inputs
Background Details
Serialization and deserialization refer to the process of taking program-internal object-related data, packaging it in a way that allows the data to be externally stored or transferred ("serialization"), then extracting the serialized data to reconstruct the original object ("deserialization").
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 life cycle at which
introduction
may occur, while the Note provides a typical scenario related to introduction during the
given
phase.
Phase
Note
Architecture and Design
OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Implementation
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
Java
(Undetermined Prevalence)
Ruby
(Undetermined Prevalence)
PHP
(Undetermined Prevalence)
Python
(Undetermined Prevalence)
JavaScript
(Undetermined Prevalence)
Technologies
Class: Not Technology-Specific
(Undetermined Prevalence)
Class: ICS/OT
(Often Prevalent)
AI/ML
(Often Prevalent)
Likelihood Of Exploit
Medium
Demonstrative Examples
Example 1
This code snippet deserializes an object from a file and uses it as a UI button:
(bad code)
Example Language:
Java
try {
File file = new File("object.obj");
ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
javax.swing.JButton button = (javax.swing.JButton) in.readObject();
in.close();
This code does not attempt to verify the source or contents of the file before deserializing it. An attacker may be able to replace the intended file with a file that contains arbitrary malicious code which will be executed when the button is pressed.
To mitigate this, explicitly define final readObject() to prevent deserialization. An example of this is:
(good code)
Example Language:
Java
private final void readObject(ObjectInputStream in) throws java.io.IOException {
throw new java.io.IOException("Cannot be deserialized"); }
Example 2
In Python, the Pickle library handles the serialization and deserialization processes. In this example derived from [
REF-467
], the code receives and parses data, and afterwards tries to authenticate a user based on validating a token.
(bad code)
Example Language:
Python
try {
class ExampleProtocol(protocol.Protocol):
def dataReceived(self, data):
# Code that would be here would parse the incoming data
# After receiving headers, call confirmAuth() to authenticate
def confirmAuth(self, headers):
try:
token = cPickle.loads(base64.b64decode(headers['AuthToken']))
if not check_hmac(token['signature'], token['data'], getSecretKey()):
raise AuthFail
self.secure_data = token['data']
except:
raise AuthFail
Unfortunately, the code does not verify that the incoming data is legitimate. An attacker can construct a illegitimate, serialized object "AuthToken" that instantiates one of Python's subprocesses to execute arbitrary commands. For instance,the attacker could construct a pickle that leverages Python's subprocess module, which spawns new processes and includes a number of arguments for various uses. Since Pickle allows objects to define the process for how they should be unpickled, the attacker can direct the unpickle process to call Popen in the subprocess module and execute /bin/sh.
Selected Observed
Examples
Note: this is a curated list of examples for users to understand the variety of ways in which this
weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.
Reference
Description
CVE-2024-37052
insecure deserialization in platform for managing AI/ML applications and models allows code execution via a crafted pickled object in a model file
CVE-2024-37288
deserialization of untrusted YAML data in dashboard for data query and visualization of Elasticsearch data
CVE-2024-9314
PHP object injection in WordPress plugin for AI-based SEO
CVE-2019-12799
chain: bypass of untrusted deserialization issue (
CWE-502
) by using an assumed-trusted class (
CWE-183
CVE-2015-8103
Deserialization issue in commonly-used Java library allows remote execution.
CVE-2015-4852
Deserialization issue in commonly-used Java library allows remote execution.
CVE-2013-1465
Use of PHP unserialize function on untrusted input allows attacker to modify application configuration.
CVE-2012-3527
Use of PHP unserialize function on untrusted input in content management system might allow code execution.
CVE-2012-0911
Use of PHP unserialize function on untrusted input in content management system allows code execution using a crafted cookie value.
CVE-2012-0911
Content management system written in PHP allows unserialize of arbitrary objects, possibly allowing code execution.
CVE-2011-2520
Python script allows local users to execute code via pickled data.
CVE-2012-4406
Unsafe deserialization using pickle in a Python script.
CVE-2003-0791
Web browser allows execution of native methods via a crafted string to a JavaScript function that deserializes the string.
Weakness Ordinalities
Ordinality
Description
Primary
(where the weakness exists independent of other weaknesses)
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
Detection
Methods
Method
Details
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
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.
858
The CERT Oracle Secure Coding Standard for Java (2011) Chapter 15 - Serialization (SER)
MemberOf
View - 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).
884
CWE Cross-section
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
994
SFP Secondary Cluster: Tainted Input to Variable
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1034
OWASP Top Ten 2017 Category A8 - Insecure Deserialization
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1148
SEI CERT Oracle Secure Coding Standard for Java - Guidelines 14. Serialization (SER)
MemberOf
View - 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
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1308
CISQ Quality Measures - Security
MemberOf
View - 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
View - 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).
1340
CISQ Data Protection Measures
MemberOf
View - 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
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1354
OWASP Top Ten 2021 Category A08:2021 - Software and Data Integrity Failures
MemberOf
View - 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
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1415
Comprehensive Categorization: Resource Control
MemberOf
View - 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
View - 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
MemberOf
View - 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).
1435
Weaknesses in the 2025 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
1443
OWASP Top Ten 2025 Category A08:2025 - Software or Data Integrity Failures
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.
Notes
Maintenance
The relationships between
CWE-502
and
CWE-915
need further exploration.
CWE-915
is more narrowly scoped to object modification, and is not necessarily used for deserialization.
Taxonomy
Mappings
Mapped Taxonomy Name
Node ID
Fit
Mapped Node Name
CLASP
Deserialization of untrusted data
The CERT Oracle Secure Coding Standard for Java (2011)
SER01-J
Do not deviate from the proper signatures of serialization methods
The CERT Oracle Secure Coding Standard for Java (2011)
SER03-J
Do not serialize unencrypted, sensitive data
The CERT Oracle Secure Coding Standard for Java (2011)
SER06-J
Make defensive copies of private mutable components during deserialization
The CERT Oracle Secure Coding Standard for Java (2011)
SER08-J
Do not use the default serialized form for implementation defined invariants
Software Fault Patterns
SFP25
Tainted input to variable
Related Attack Patterns
CAPEC-ID
Attack Pattern Name
CAPEC-586
Object Injection
References
[REF-18]
Secure Software, Inc..
"The CLASP Application Security Process".
2005.
>.

URL validated: 2024-11-17
[REF-461]
Matthias Kaiser.
"Exploiting Deserialization Vulnerabilities in Java".
2015-10-28.
>.

URL validated: 2023-04-07
[REF-462]
Sam Thomas.
"PHP unserialization vulnerabilities: What are we missing?".
2015-08-27.
>.

URL validated: 2023-04-07
[REF-463]
Gabriel Lawrence and Chris Frohoff.
"Marshalling Pickles: How deserializing objects can ruin your day".
2015-01-28.
>.

URL validated: 2023-04-07
[REF-464]
Heine Deelstra.
"Unserializing user-supplied data, a bad idea".
2010-08-25.
>.

URL validated: 2023-04-07
[REF-465]
Manish S. Saindane.
"Black Hat EU 2010 - Attacking Java Serialized Communication".
2010-04-26.
>.

URL validated: 2023-04-07
[REF-466]
Nadia Alramli.
"Why Python Pickle is Insecure".
2009-09-09.
>.

URL validated: 2023-04-07
[REF-467]
Nelson Elhage.
"Exploiting misuse of Python's "pickle"".
2011-03-20.
>.
[REF-468]
Chris Frohoff.
"Deserialize My Shorts: Or How I Learned to Start Worrying and Hate Java Object Deserialization".
2016-03-21.
>.

URL validated: 2023-04-07
[REF-1481]
D3FEND.
"D3FEND: Application Layer Firewall".
>.

URL validated: 2025-09-06
Content
History
Submissions
Submission Date
Submitter
Organization
2006-07-19
(CWE Draft 3, 2006-07-19)
CLASP
Contributions
Contribution Date
Contributor
Organization
2024-02-29
(CWE 4.16, 2024-11-19)
Abhi Balakrishnan
Contributed usability diagram concepts used by the CWE team
Modifications
Modification Date
Modifier
Organization
2025-12-11
(CWE 4.19, 2025-12-11)
CWE Content Team
MITRE
updated Applicable_Platforms, Observed_Examples, Relationships, Weakness_Ordinalities
2025-09-09
(CWE 4.18, 2025-09-09)
CWE Content Team
MITRE
updated Observed_Examples, Potential_Mitigations, References
2024-11-19
(CWE 4.16, 2024-11-19)
CWE Content Team
MITRE
updated Common_Consequences, Description, Diagram, Potential_Mitigations, Relationships
2023-06-29
CWE Content Team
MITRE
updated Mapping_Notes, Relationships
2023-04-27
CWE Content Team
MITRE
updated Detection_Factors, References, Relationships
2023-01-31
CWE Content Team
MITRE
updated Description
2022-10-13
CWE Content Team
MITRE
updated Applicable_Platforms
2022-06-28
CWE Content Team
MITRE
updated Relationships
2021-10-28
CWE Content Team
MITRE
updated Relationships
2021-07-20
CWE Content Team
MITRE
updated Relationships
2020-12-10
CWE Content Team
MITRE
updated Relationships
2020-08-20
CWE Content Team
MITRE
updated Relationships
2020-06-25
CWE Content Team
MITRE
updated Alternate_Terms, Potential_Mitigations
2020-02-24
CWE Content Team
MITRE
updated Observed_Examples, References, Relationships
2019-09-19
CWE Content Team
MITRE
updated Relationships
2019-06-20
CWE Content Team
MITRE
updated Type
2019-01-03
CWE Content Team
MITRE
updated Related_Attack_Patterns, Relationships, Taxonomy_Mappings
2018-03-27
CWE Content Team
MITRE
updated Relationships
2017-11-08
CWE Content Team
MITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Modes_of_Introduction, Potential_Mitigations, References, Relationships
2017-05-03
CWE Content Team
MITRE
updated Applicable_Platforms, Demonstrative_Examples, Description, Potential_Mitigations, References
2015-12-07
CWE Content Team
MITRE
updated Observed_Examples, References, Relationships
2014-07-30
CWE Content Team
MITRE
updated Relationships, Taxonomy_Mappings
2013-02-21
CWE Content Team
MITRE
updated Alternate_Terms, Applicable_Platforms, Background_Details, Common_Consequences, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, Relationships
2012-10-30
CWE Content Team
MITRE
updated Demonstrative_Examples
2012-05-11
CWE Content Team
MITRE
updated Relationships, Taxonomy_Mappings
2011-06-01
CWE Content Team
MITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2009-10-29
CWE Content Team
MITRE
updated Description, Other_Notes, Potential_Mitigations
2008-09-08
CWE Content Team
MITRE
updated Common_Consequences, Description, Relationships, Other_Notes, Taxonomy_Mappings
2008-07-01
Eric Dalci
Cigital
updated Time_of_Introduction
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Page Last Updated:
January 21, 2026
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