CWE-494 Detail

CWE-494

Download of Code Without Integrity Check
MEDIUM
Draft
2006-07-19 00:00 +00:00
2024-02-29 00:00 +00:00

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Download of Code Without Integrity Check

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.

Extended Description

An attacker can execute malicious code by compromising the host server, performing DNS spoofing, or modifying the code in transit.

Informations

Modes Of Introduction

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

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Common Consequences

Scope Impact Likelihood
Integrity
Availability
Confidentiality
Other
Execute Unauthorized Code or Commands, Alter Execution Logic, Other

Note: 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.

Observed Examples

Reference Description
CVE-2019-9534Satellite phone does not validate its firmware image.
CVE-2021-22909Chain: 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).
CVE-2008-3438OS does not verify authenticity of its own updates.
CVE-2008-3324online poker client does not verify authenticity of its own updates.
CVE-2001-1125anti-virus product does not verify automatic updates for itself.
CVE-2002-0671VOIP phone downloads applications from web sites without verifying integrity.

Potential Mitigations

Phases : Implementation
Perform proper forward and reverse DNS lookups to detect DNS spoofing.
Phases : 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.


Phases : Architecture and Design

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

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].

Phases : Architecture and Design // Operation
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.
Phases : Architecture and Design // Operation

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.


Detection Methods

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.


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.)
Effectiveness : High

Vulnerability Mapping Notes

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.

Related Attack Patterns

CAPEC-ID Attack Pattern Name
CAPEC-184 Software Integrity Attack
An attacker initiates a series of events designed to cause a user, program, server, or device to perform actions which undermine the integrity of software code, device data structures, or device firmware, achieving the modification of the target's integrity to achieve an insecure state.
CAPEC-185 Malicious Software Download
An attacker uses deceptive methods to cause a user or an automated process to download and install dangerous code that originates from an attacker controlled source. There are several variations to this strategy of attack.
CAPEC-186 Malicious Software Update
An adversary uses deceptive methods to cause a user or an automated process to download and install dangerous code believed to be a valid update that originates from an adversary controlled source.
CAPEC-187 Malicious Automated Software Update via Redirection
An attacker exploits two layers of weaknesses in server or client software for automated update mechanisms to undermine the integrity of the target code-base. The first weakness involves a failure to properly authenticate a server as a source of update or patch content. This type of weakness typically results from authentication mechanisms which can be defeated, allowing a hostile server to satisfy the criteria that establish a trust relationship. The second weakness is a systemic failure to validate the identity and integrity of code downloaded from a remote location, hence the inability to distinguish malicious code from a legitimate update.
CAPEC-533 Malicious Manual Software Update
An attacker introduces malicious code to the victim's system by altering the payload of a software update, allowing for additional compromise or site disruption at the victim location. These manual, or user-assisted attacks, vary from requiring the user to download and run an executable, to as streamlined as tricking the user to click a URL. Attacks which aim at penetrating a specific network infrastructure often rely upon secondary attack methods to achieve the desired impact. Spamming, for example, is a common method employed as an secondary attack vector. Thus the attacker has in their arsenal a choice of initial attack vectors ranging from traditional SMTP/POP/IMAP spamming and its varieties, to web-application mechanisms which commonly implement both chat and rich HTML messaging within the user interface.
CAPEC-538 Open-Source Library Manipulation
Adversaries implant malicious code in open source software (OSS) libraries to have it widely distributed, as OSS is commonly downloaded by developers and other users to incorporate into software development projects. The adversary can have a particular system in mind to target, or the implantation can be the first stage of follow-on attacks on many systems.
CAPEC-657 Malicious Automated Software Update via Spoofing
An attackers uses identify or content spoofing to trick a client into performing an automated software update from a malicious source. A malicious automated software update that leverages spoofing can include content or identity spoofing as well as protocol spoofing. Content or identity spoofing attacks can trigger updates in software by embedding scripted mechanisms within a malicious web page, which masquerades as a legitimate update source. Scripting mechanisms communicate with software components and trigger updates from locations specified by the attackers' server. The result is the client believing there is a legitimate software update available but instead downloading a malicious update from the attacker.
CAPEC-662 Adversary in the Browser (AiTB)

An adversary exploits security vulnerabilities or inherent functionalities of a web browser, in order to manipulate traffic between two endpoints.

CAPEC-691 Spoof Open-Source Software Metadata

An adversary spoofs open-source software metadata in an attempt to masquerade malicious software as popular, maintained, and trusted.

CAPEC-692 Spoof Version Control System Commit Metadata

An adversary spoofs metadata pertaining to a Version Control System (VCS) (e.g., Git) repository's commits to deceive users into believing that the maliciously provided software is frequently maintained and originates from a trusted source.

CAPEC-693 StarJacking

An adversary spoofs software popularity metadata to deceive users into believing that a maliciously provided package is widely used and originates from a trusted source.

CAPEC-695 Repo Jacking

An adversary takes advantage of the redirect property of directly linked Version Control System (VCS) repositories to trick users into incorporating malicious code into their applications.

Notes

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.

References

REF-454

Introduction to Code Signing
Microsoft.
http://msdn.microsoft.com/en-us/library/ms537361(VS.85).aspx

REF-455

Authenticode
Microsoft.
http://msdn.microsoft.com/en-us/library/ms537359(v=VS.85).aspx

REF-456

Code Signing Guide
Apple.
https://web.archive.org/web/20080724215143/http://developer.apple.com/documentation/Security/Conceptual/CodeSigningGuide/Introduction/chapter_1_section_1.html

REF-457

Secure Software Updates: Disappointments and New Challenges
Anthony Bellissimo, John Burgess, Kevin Fu.
http://prisms.cs.umass.edu/~kevinfu/papers/secureupdates-hotsec06.pdf

REF-44

24 Deadly Sins of Software Security
Michael Howard, David LeBlanc, John Viega.

REF-459

Top 25 Series - Rank 20 - Download of Code Without Integrity Check
Johannes Ullrich.
https://www.sans.org/blog/top-25-series-rank-20-download-of-code-without-integrity-check/

REF-76

Least Privilege
Sean Barnum, Michael Gegick.
https://web.archive.org/web/20211209014121/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/least-privilege

REF-18

The CLASP Application Security Process
Secure Software, Inc..
https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf

Submission

Name Organization Date Date Release Version
CLASP 2006-07-19 +00:00 2006-07-19 +00:00 Draft 3

Modifications

Name Organization Date Comment
Eric Dalci Cigital 2008-07-01 +00:00 updated Time_of_Introduction
CWE Content Team MITRE 2008-09-08 +00:00 updated Relationships, Other_Notes, Taxonomy_Mappings
CWE Content Team MITRE 2009-01-12 +00:00 updated Applicable_Platforms, Common_Consequences, Description, Name, Other_Notes, Potential_Mitigations, References, Relationships, Research_Gaps, Type
CWE Content Team MITRE 2009-03-10 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2009-07-27 +00:00 updated Description, Observed_Examples, Related_Attack_Patterns
CWE Content Team MITRE 2010-02-16 +00:00 updated Detection_Factors, References, Relationships
CWE Content Team MITRE 2010-04-05 +00:00 updated Applicable_Platforms
CWE Content Team MITRE 2010-06-21 +00:00 updated Common_Consequences, Detection_Factors, Potential_Mitigations, References
CWE Content Team MITRE 2010-09-27 +00:00 updated Potential_Mitigations, References
CWE Content Team MITRE 2010-12-13 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2011-03-29 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences, Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2011-06-27 +00:00 updated Relationships
CWE Content Team MITRE 2011-09-13 +00:00 updated Potential_Mitigations, References
CWE Content Team MITRE 2012-05-11 +00:00 updated References, Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2012-10-30 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2014-07-30 +00:00 updated Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2017-11-08 +00:00 updated Modes_of_Introduction, References, Relationships
CWE Content Team MITRE 2019-01-03 +00:00 updated Taxonomy_Mappings
CWE Content Team MITRE 2019-06-20 +00:00 updated Related_Attack_Patterns, Relationships
CWE Content Team MITRE 2020-02-24 +00:00 updated Demonstrative_Examples, Relationships
CWE Content Team MITRE 2020-08-20 +00:00 updated Relationships
CWE Content Team MITRE 2020-12-10 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2021-03-15 +00:00 updated References, Related_Attack_Patterns
CWE Content Team MITRE 2021-07-20 +00:00 updated Demonstrative_Examples
CWE Content Team MITRE 2021-10-28 +00:00 updated Observed_Examples, Relationships
CWE Content Team MITRE 2022-10-13 +00:00 updated References, Related_Attack_Patterns
CWE Content Team MITRE 2023-01-31 +00:00 updated Related_Attack_Patterns
CWE Content Team MITRE 2023-04-27 +00:00 updated Detection_Factors, References, Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2024-02-29 +00:00 updated Demonstrative_Examples, Relationships