CWE-766: Critical Data Element Declared Public

Code Examples & CVEs

Demonstrative Examples

The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.

Instead, the critical data should be declared private.

BadC++

public: char* password;

The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.

Instead, the critical data should be declared private.

GoodC++

private: char* password;

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.

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.

BadC++

#define MAX_PASSWORD_LENGTH 15#define MAX_USERNAME_LENGTH 15                      class UserAccount{                         public:                               UserAccount(char *username, char *password){if ((strlen(username) > MAX_USERNAME_LENGTH) ||(strlen(password) > MAX_PASSWORD_LENGTH)) {ExitError("Invalid username or password");}strcpy(this->username, username);strcpy(this->password, password);}                                                                                    int authorizeAccess(char *username, char *password){                               if ((strlen(username) > MAX_USERNAME_LENGTH) ||(strlen(password) > MAX_PASSWORD_LENGTH)) {ExitError("Invalid username or password");}                                  // if the username and password in the input parameters are equal to                                                                                                      // the username and password of this account class then authorize access                                  if (strcmp(this->username, username) ||strcmp(this->password, password))return 0;                                                                    // otherwise do not authorize access                                  elsereturn 1;                                                           }                            char username[MAX_USERNAME_LENGTH+1];char password[MAX_PASSWORD_LENGTH+1];                      };

GoodC++

class UserAccount{public:...                                            private:char username[MAX_USERNAME_LENGTH+1];char password[MAX_PASSWORD_LENGTH+1];};

Observed CVE Examples (1)

CVE-2010-3860

variables declared public allow remote read of system properties such as user name and home directory.

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-766 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-766, Critical Data Element Declared Public, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Critical Data Element Declared Public during Implementation

MITRE associates mitigation with Implementation; documented detection approaches include Automated Static Analysis; recorded impacts include Read Application Data, Modify Application Data, and Reduce Maintainability. Use these source-defined anchors to turn CWE-766 into implementation, review, and verification checks for the affected component.

CWE-766: Critical Data Element Declared Public — MITRE CWE

Triage CWE-766 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-766, Critical Data Element Declared Public, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-766

Apply MITRE's full root-cause mapping guidance when using CWE-766, Critical Data Element Declared Public. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-766 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-766, Critical Data Element Declared Public. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-766: Critical Data Element Declared Public?+

CWE-766: Critical Data Element Declared Public is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product declares a critical variable, field, or member to be public when intended security policy requires it to be private. This issue makes it more difficult to maintain the product, which indirectly affects security by making it more difficult or time-consuming to find and/or fix vulnerabilities. It also might make it easier to introduce vulnerabilities.

What are the security consequences of Critical Data Element Declared Public?+

If exploited, CWE-766 (Critical Data Element Declared Public) it can compromise Integrity, Confidentiality and Other, leading to outcomes such as Read Application Data, Modify Application Data and Reduce Maintainability.

How do you prevent or mitigate Critical Data Element Declared Public?+

Recommended mitigations for CWE-766 include: 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.

Which programming languages are affected by Critical Data Element Declared Public?+

CWE-766 commonly affects C++, C# and Java. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Critical Data Element Declared Public?+

MITRE documents real CVEs mapped to CWE-766, including CVE-2010-3860. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-766 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-766: Critical Data Element Declared Public

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