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.)
CWE-15 Base Incomplete
External Control of System or Configuration Setting
This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an external source.
Definition
What is CWE-15?
This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an external source.
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.
Real-world impact
Real-world CVEs caused by CWE-15
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
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.
- 2
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.
- 3
The following Java code snippet reads a string from an HttpServletRequest and sets it as the active catalog for a database Connection.
- 4
In this example, an attacker could cause an error by providing a nonexistent catalog name or connect to an unauthorized portion of the database.
Vulnerable code example
Vulnerable C
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.
...
sethostid(argv[1]);
... Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-15
- Architecture and Design 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.
- Implementation / Architecture 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.
- Implementation / Architecture 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.
Detection signals
How to detect CWE-15
CWE-15
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Frequently asked questions What is CWE-15?
How serious is CWE-15?
What languages or platforms are affected by CWE-15?
How can I prevent CWE-15?
How does Plexicus detect and fix CWE-15?
Where can I learn more about CWE-15?
Frequently asked questions
What is CWE-15?
This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an external source.
How serious is CWE-15?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-15?
MITRE lists the following affected platforms: Not Technology-Specific, ICS/OT.
How can I prevent CWE-15?
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…
How does Plexicus detect and fix CWE-15?
Plexicus's SAST engine matches the data-flow signature for CWE-15 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-15?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/15.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-15
CWE-642 Parent
External Control of Critical State Data
This vulnerability occurs when an application stores security-sensitive state data in locations that unauthorized users can access and…
CWE-426 Sibling
Untrusted Search Path
This vulnerability occurs when an application relies on an external search path, provided by a user or environment, to find and load…
CWE-472 Sibling
External Control of Assumed-Immutable Web Parameter
This vulnerability occurs when a web application incorrectly trusts data that appears to be fixed or hidden from the user, such as values…
CWE-565 Sibling
Reliance on Cookies without Validation and Integrity Checking
This vulnerability occurs when an application uses cookies to make security decisions—like granting access or changing settings—but fails…
CWE-73 Sibling
External Control of File Name or Path
This vulnerability occurs when an application uses unvalidated user input to construct file or directory paths for filesystem operations.
Resources
Further reading
- MITRE — official CWE-15 https://cwe.mitre.org/data/definitions/15.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
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