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-766 Base Incomplete
Critical Data Element Declared Public
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's…
Definition
What is CWE-766?
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's security design.
Declaring sensitive data as public breaks fundamental security principles like encapsulation and least privilege. It directly exposes critical information, such as internal state, configuration secrets, or authentication tokens, to any other part of the codebase or, in some languages and contexts, to external actors. This creates a clear and immediate attack surface, making it trivial for an attacker to read or modify data that should be strictly controlled.
Beyond the direct security flaw, this practice severely damages code maintainability and security hygiene. It becomes difficult to track how and where this critical data is being used or altered, scattering logic that should be centralized. This "spaghetti code" effect makes identifying the root cause of bugs or vulnerabilities more time-consuming and increases the risk of introducing new security weaknesses during future development or refactoring.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-766
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variables declared public allow remote read of system properties such as user name and home directory.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.
- 2
Instead, the critical data should be declared private.
- 3
Even though this example declares the password to be private, there are other possible issues with this implementation, such as the possibility of recovering the password from process memory (CWE-257).
- 4
The following example shows a basic user account class that includes member variables for the username and password as well as a public constructor for the class and a public method to authorize access to the user account.
- 5
However, the member variables username and password are declared public and therefore will allow access and changes to the member variables to anyone with access to the object. These member variables should be declared private as shown below to prevent unauthorized access and changes.
Verwundbares Codebeispiel
Vulnerable C++
The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.
public: char* password; Sicheres Codebeispiel
Secure C++
Instead, the critical data should be declared private.
private: char* password; What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste
How to prevent CWE-766
- Implementation Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.
Erkennungssignale
How to detect CWE-766
CWE-766
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-766?
Wie gravierend ist CWE-766?
Welche Sprachen oder Plattformen sind von CWE-766 betroffen?
Wie kann ich CWE-766 verhindern?
Wie erkennt und behebt Plexicus CWE-766?
Wo erfahre ich mehr über CWE-766?
Frequently asked questions
Was ist CWE-766?
This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it should be kept private according to the application's security design.
Wie gravierend ist CWE-766?
MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.
Welche Sprachen oder Plattformen sind von CWE-766 betroffen?
MITRE lists the following affected platforms: C++, C#, Java.
Wie kann ich CWE-766 verhindern?
Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.
Wie erkennt und behebt Plexicus CWE-766?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-766 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.
Wo erfahre ich mehr über CWE-766?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/766.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-766
CWE-732 Parent
Incorrect Permission Assignment for Critical Resource
This vulnerability occurs when a system grants overly permissive access to a sensitive resource, allowing unauthorized users or processes…
CWE-1004 Sibling
Sensitive Cookie Without 'HttpOnly' Flag
This vulnerability occurs when an application stores sensitive data in a cookie but fails to set the 'HttpOnly' flag, leaving the cookie…
CWE-276 Sibling
Incorrect Default Permissions
This vulnerability occurs when software installation scripts set overly permissive file or directory access rights by default. Instead of…
CWE-277 Sibling
Insecure Inherited Permissions
This vulnerability occurs when an application sets default file or directory permissions that are too permissive, and these insecure…
CWE-278 Sibling
Insecure Preserved Inherited Permissions
This vulnerability occurs when a software product copies or extracts files while unintentionally preserving insecure permissions from…
CWE-279 Sibling
Incorrect Execution-Assigned Permissions
This vulnerability occurs when a running application incorrectly changes an object's access permissions, overriding the security settings…
CWE-281 Sibling
Improper Preservation of Permissions
This vulnerability occurs when a system fails to correctly maintain file or object permissions during operations like copying, sharing, or…
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