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External Control of System or Configuration Setting

Incomplete Base
Structure: Simple
Description

This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an external source.

Extended Description

When system settings like file paths, feature flags, or environment variables can be controlled by an external user, it breaks the fundamental trust between the application and its configuration. Attackers can exploit this to disrupt services, bypass security controls, or force the application to execute unintended and potentially malicious actions, leading to data loss or system compromise. Preventing this requires rigorous validation of all configuration inputs and enforcing strict separation between user data and system controls. While SAST tools can catch the pattern, Plexicus uses AI to analyze the data flow and suggest the precise code fix—such as implementing allowlists or moving configurations to secure, internal sources—saving hours of manual remediation work across your codebase.
Common Consequences 1
Scope: Other

Impact: Varies by Context
Detection Methods 1
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: Architecture and Design

Strategy: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Phase: ImplementationArchitecture and Design
Because setting manipulation covers a diverse set of functions, any attempt at illustrating it will inevitably be incomplete. Rather than searching for a tight-knit relationship between the functions addressed in the setting manipulation category, take a step back and consider the sorts of system values that an attacker should not be allowed to control.
Phase: ImplementationArchitecture and Design
In general, do not allow user-provided or otherwise untrusted data to control sensitive values. The leverage that an attacker gains by controlling these values is not always immediately obvious, but do not underestimate the creativity of the attacker.
Demonstrative Examples 2
The following C code accepts a number as one of its command line parameters and sets it as the host ID of the current machine.

Code Example:

Bad
C
c
Although a process must be privileged to successfully invoke sethostid(), unprivileged users may be able to invoke the program. The code in this example allows user input to directly control the value of a system setting. If an attacker provides a malicious value for host ID, the attacker can misidentify the affected machine on the network or cause other unintended behavior.
The following Java code snippet reads a string from an HttpServletRequest and sets it as the active catalog for a database Connection.

Code Example:

Bad
Java
java
In this example, an attacker could cause an error by providing a nonexistent catalog name or connect to an unauthorized portion of the database.
References 1
Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors
Katrina Tsipenyuk, Brian Chess, and Gary McGraw
NIST Workshop on Software Security Assurance Tools Techniques and Metrics • NIST
07-11-2005
https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
ID: REF-6
Applicable Platforms
Technologies:
Not Technology-Specific : UndeterminedICS/OT : Undetermined
Modes of Introduction
Implementation
Implementation
Related Attack Patterns
Related Weaknesses
ChildOf: External Control of Critical State Data (CWE-642)
ChildOf: Externally Controlled Reference to a Resource in Another Sphere (CWE-610)
ChildOf: Improper Input Validation (CWE-20)
Taxonomy Mapping
  • 7 Pernicious Kingdoms
  • Software Fault Patterns