The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.
An attacker can execute malicious code by compromising the host server, performing DNS spoofing, or modifying the code in transit.

Primary

Architecture and Design
OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.

Implementation

Medium

Integrity
Availability
Confidentiality
Other
Execute Unauthorized Code or Commands
Alter Execution Logic
Other
Executing untrusted code could compromise the control flow of the program. The untrusted code could execute attacker-controlled commands, read or modify sensitive resources, or prevent the software from functioning correctly for legitimate users.

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.
Specifically, manual static analysis is typically required to find the behavior that triggers the download of code, and to determine whether integrity-checking methods are in use.

These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.

Black Box

Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic.
Attach the monitor to the process and also sniff the network connection. Trigger features related to product updates or plugin installation, which is likely to force a code download. Monitor when files are downloaded and separately executed, or if they are otherwise read back into the process. Look for evidence of cryptographic library calls that use integrity checking.

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.)
High

Implementation
Perform proper forward and reverse DNS lookups to detect DNS spoofing.
This is only a partial solution since it will not prevent your code from being modified on the hosting site or in transit.

Architecture and Design
Operation

Encrypt the code with a reliable encryption scheme before transmitting.
This will only be a partial solution, since it will not detect DNS spoofing and it will not prevent your code from being modified on the hosting site.

Architecture and Design
Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
Speficially, it may be helpful to use tools or frameworks to perform integrity checking on the transmitted code.

When providing the code that is to be downloaded, such as for automatic updates of the software, then use cryptographic signatures for the code and modify the download clients to verify the signatures. Ensure that the implementation does not contain CWE-295, CWE-320, CWE-347, and related weaknesses.
Use code signing technologies such as Authenticode. See references [REF-454] [REF-455] [REF-456].

Architecture and Design
Operation
Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Architecture and Design
Operation
Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
Be careful to avoid CWE-243 and other weaknesses related to jails.

Limited
The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

This example loads an external class from a local subdirectory.

URL[] classURLs= new URL[]{new URL("file:subdir/")};URLClassLoader loader = new URLClassLoader(classURLs);Class loadedClass = Class.forName("loadMe", true, loader);

This code does not ensure that the class loaded is the intended one, for example by verifying the class's checksum. An attacker may be able to modify the class file to execute malicious code.

This code includes an external script to get database credentials, then authenticates a user against the database, allowing access to the application.

//assume the password is already encrypted, avoiding CWE-312

function authenticate($username,$password){
include("http://external.example.com/dbInfo.php");

//dbInfo.php makes $dbhost, $dbuser, $dbpass, $dbname available
mysql_connect($dbhost, $dbuser, $dbpass) or die ('Error connecting to mysql');mysql_select_db($dbname);$query = 'Select * from users where username='.$username.' And password='.$password;$result = mysql_query($query);
if(mysql_numrows($result) == 1){mysql_close();return true;}else{mysql_close();return false;}
}

This code does not verify that the external domain accessed is the intended one. An attacker may somehow cause the external domain name to resolve to an attack server, which would provide the information for a false database. The attacker may then steal the usernames and encrypted passwords from real user login attempts, or simply allow themself to access the application without a real user account.
This example is also vulnerable to an Adversary-in-the-Middle AITM (CWE-300) attack.

CVE-2019-9534
Satellite phone does not validate its firmware image.
https://www.cve.org/CVERecord?id=CVE-2019-9534

CVE-2021-22909
Chain: router's firmware update procedure uses curl with "-k" (insecure) option that disables certificate validation (CWE-295), allowing adversary-in-the-middle (AITM) compromise with a malicious firmware image (CWE-494).
https://www.cve.org/CVERecord?id=CVE-2021-22909

CVE-2008-3438
OS does not verify authenticity of its own updates.
https://www.cve.org/CVERecord?id=CVE-2008-3438

CVE-2008-3324
online poker client does not verify authenticity of its own updates.
https://www.cve.org/CVERecord?id=CVE-2008-3324

CVE-2001-1125
anti-virus product does not verify automatic updates for itself.
https://www.cve.org/CVERecord?id=CVE-2001-1125

CVE-2002-0671
VOIP phone downloads applications from web sites without verifying integrity.
https://www.cve.org/CVERecord?id=CVE-2002-0671

Invoking untrusted mobile code

SEC06-J
Do not rely on the default automatic signature verification provided by URLClassLoader and java.util.jar

SFP27
Tainted input to environment

Allowed
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.
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.

This is critical for mobile code, but it is likely to become more and more common as developers continue to adopt automated, network-based product distributions and upgrades. Software-as-a-Service (SaaS) might introduce additional subtleties. Common exploitation scenarios may include ad server compromises and bad upgrades.

CLASP
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Other_Notes, Taxonomy_Mappings

CWE Content Team
MITRE
2009-01-12
updated Applicable_Platforms, Common_Consequences, Description, Name, Other_Notes, Potential_Mitigations, References, Relationships, Research_Gaps, Type

CWE Content Team
MITRE
2009-03-10
updated Potential_Mitigations

CWE Content Team
MITRE
2009-07-27
updated Description, Observed_Examples, Related_Attack_Patterns

CWE Content Team
MITRE
2010-02-16
updated Detection_Factors, References, Relationships

CWE Content Team
MITRE
2010-04-05
updated Applicable_Platforms

CWE Content Team
MITRE
2010-06-21
updated Common_Consequences, Detection_Factors, Potential_Mitigations, References

CWE Content Team
MITRE
2010-09-27
updated Potential_Mitigations, References

CWE Content Team
MITRE
2010-12-13
updated Potential_Mitigations

CWE Content Team
MITRE
2011-03-29
updated Demonstrative_Examples

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2011-06-27
updated Relationships

CWE Content Team
MITRE
2011-09-13
updated Potential_Mitigations, References

CWE Content Team
MITRE
2012-05-11
updated References, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2012-10-30
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Modes_of_Introduction, References, Relationships

CWE Content Team
MITRE
2019-01-03
updated Taxonomy_Mappings

CWE Content Team
MITRE
2019-06-20
updated Related_Attack_Patterns, Relationships

CWE Content Team
MITRE
2020-02-24
updated Demonstrative_Examples, Relationships

CWE Content Team
MITRE
2020-08-20
updated Relationships

CWE Content Team
MITRE
2020-12-10
updated Demonstrative_Examples

CWE Content Team
MITRE
2021-03-15
updated References, Related_Attack_Patterns

CWE Content Team
MITRE
2021-07-20
updated Demonstrative_Examples

CWE Content Team
MITRE
2021-10-28
updated Observed_Examples, Relationships

CWE Content Team
MITRE
2022-10-13
updated References, Related_Attack_Patterns

CWE Content Team
MITRE
2023-01-31
updated Related_Attack_Patterns

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, References, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2024-02-29
4.14
2024-02-29
updated Demonstrative_Examples, Relationships

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated Potential_Mitigations, References

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Relationships, Weakness_Ordinalities

Mobile Code: Invoking Untrusted Mobile Code
Download of Untrusted Mobile Code Without Integrity Check