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CWE-200: Exposure of Sensitive Information to an Unauthorized Actor (4.17)

Weakness ID: 200

Description

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

Extended Description

There are many different kinds of mistakes that introduce information exposures. The severity of the error can range widely, depending on the context in which the product operates, the type of sensitive information that is revealed, and the benefits it may provide to an attacker. Some kinds of sensitive information include:

• private, personal information, such as personal messages, financial data, health records, geographic location, or contact details
• system status and environment, such as the operating system and installed packages
• business secrets and intellectual property
• network status and configuration
• the product's own code or internal state
• metadata, e.g. logging of connections or message headers
• indirect information, such as a discrepancy between two internal operations that can be observed by an outsider

Information might be sensitive to different parties, each of which may have their own expectations for whether the information should be protected. These parties include:

• the product's own users
• people or organizations whose information is created or used by the product, even if they are not direct product users
• the product's administrators, including the admins of the system(s) and/or networks on which the product operates
• the developer

Information exposures can occur in different ways:

• the code explicitly inserts sensitive information into resources or messages that are intentionally made accessible to unauthorized actors, but should not contain the information - i.e., the information should have been "scrubbed" or "sanitized"
• a different weakness or mistake indirectly inserts the sensitive information into resources, such as a web script error revealing the full system path of the program.
• the code manages resources that intentionally contain sensitive information, but the resources are unintentionally made accessible to unauthorized actors. In this case, the information exposure is resultant - i.e., a different weakness enabled the access to the information in the first place.

It is common practice to describe any loss of confidentiality as an "information exposure," but this can lead to overuse of CWE-200 in CWE mapping. From the CWE perspective, loss of confidentiality is a technical impact that can arise from dozens of different weaknesses, such as insecure file permissions or out-of-bounds read. CWE-200 and its lower-level descendants are intended to cover the mistakes that occur in behaviors that explicitly manage, store, transfer, or cleanse sensitive information.

Alternate Terms

This term is frequently used in vulnerability advisories to describe a consequence or technical impact, for any vulnerability that has a loss of confidentiality. Often,

can be misused to represent the loss of confidentiality, even when the mistake - i.e., the weakness - is not directly related to the mishandling of the information itself, such as an out-of-bounds read that accesses sensitive memory contents; here, the out-of-bounds read is the primary weakness, not the disclosure of the memory. In addition, this phrase is also used frequently in policies and legal documents, but it does not refer to any disclosure of security-relevant information.

This is a frequently used term, however the "leak" term has multiple uses within security. In some cases it deals with the accidental exposure of information from a different weakness, but in other cases (such as "memory leak"), this deals with improper tracking of resources, which can lead to exhaustion. As a result, CWE is actively avoiding usage of the "leak" term.

Common Consequences

Read Application Data

Potential Mitigations

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.

Relationships

Relevant to the view "Research Concepts" (View-1000)

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)

Modes Of Introduction

Applicable Platforms

Class: Not Language-Specific (Undetermined Prevalence)

Class: Mobile (Undetermined Prevalence)

Likelihood Of Exploit

Demonstrative Examples

Example 1

The following code checks validity of the supplied username and password and notifies the user of a successful or failed login.

(bad code)

Example Language: Perl 

my $username=param('username');

my $password=param('password');

if (IsValidUsername($username) == 1)

{

if (IsValidPassword($username, $password) == 1)

{

print "Login Successful";

}

else

{

print "Login Failed - incorrect password";

}

}

else

{

print "Login Failed - unknown username";

}

In the above code, there are different messages for when an incorrect username is supplied, versus when the username is correct but the password is wrong. This difference enables a potential attacker to understand the state of the login function, and could allow an attacker to discover a valid username by trying different values until the incorrect password message is returned. In essence, this makes it easier for an attacker to obtain half of the necessary authentication credentials.

While this type of information may be helpful to a user, it is also useful to a potential attacker. In the above example, the message for both failed cases should be the same, such as:

"Login Failed - incorrect username or password"

Example 2

This code tries to open a database connection, and prints any exceptions that occur.

(bad code)

Example Language: PHP 

try {

openDbConnection();

}

catch (Exception $e) {

echo 'Caught exception: ', $e->getMessage(), '\n';
echo 'Check credentials in config file at: ', $Mysql_config_location, '\n';

}

If an exception occurs, the printed message exposes the location of the configuration file the script is using. An attacker can use this information to target the configuration file (perhaps exploiting a Path Traversal weakness). If the file can be read, the attacker could gain credentials for accessing the database. The attacker may also be able to replace the file with a malicious one, causing the application to use an arbitrary database.

Example 3

In the example below, the method getUserBankAccount retrieves a bank account object from a database using the supplied username and account number to query the database. If an SQLException is raised when querying the database, an error message is created and output to a log file.

(bad code)

Example Language: Java 

public BankAccount getUserBankAccount(String username, String accountNumber) {

BankAccount userAccount = null;

String query = null;

try {

if (isAuthorizedUser(username)) {

query = "SELECT * FROM accounts WHERE owner = "
+ username + " AND accountID = " + accountNumber;
DatabaseManager dbManager = new DatabaseManager();
Connection conn = dbManager.getConnection();
Statement stmt = conn.createStatement();
ResultSet queryResult = stmt.executeQuery(query);
userAccount = (BankAccount)queryResult.getObject(accountNumber);

}

} catch (SQLException ex) {

String logMessage = "Unable to retrieve account information from database,\nquery: " + query;
Logger.getLogger(BankManager.class.getName()).log(Level.SEVERE, logMessage, ex);

}

return userAccount;

}

The error message that is created includes information about the database query that may contain sensitive information about the database or query logic. In this case, the error message will expose the table name and column names used in the database. This data could be used to simplify other attacks, such as SQL injection (CWE-89) to directly access the database.

Example 4

This code stores location information about the current user:

(bad code)

Example Language: Java 

locationClient = new LocationClient(this, this, this);

locationClient.connect();

currentUser.setLocation(locationClient.getLastLocation());

catch (Exception e) {

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Sorry, this application has experienced an error.");
AlertDialog alert = builder.create();
alert.show();
Log.e("ExampleActivity", "Caught exception: " + e + " While on User:" + User.toString());

When the application encounters an exception it will write the user object to the log. Because the user object contains location information, the user's location is also written to the log.

Example 5

The following is an actual MySQL error statement:

(result)

Example Language: SQL 

Warning: mysql_pconnect(): Access denied for user: 'root@localhost' (Using password: N1nj4) in /usr/local/www/wi-data/includes/database.inc on line 4

The error clearly exposes the database credentials.

Example 6

This code displays some information on a web page.

(bad code)

Example Language: JSP 

Social Security Number: <%= ssn %></br>Credit Card Number: <%= ccn %>

The code displays a user's credit card and social security numbers, even though they aren't absolutely necessary.

Example 7

The following program changes its behavior based on a debug flag.

(bad code)

Example Language: JSP 

<% if (Boolean.getBoolean("debugEnabled")) {

%>
User account number: <%= acctNo %>
<%
} %>

The code writes sensitive debug information to the client browser if the "debugEnabled" flag is set to true .

Example 8

This code uses location to determine the user's current US State location.

First the application must declare that it requires the ACCESS_FINE_LOCATION permission in the application's manifest.xml:

(bad code)

Example Language: XML 

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

During execution, a call to getLastLocation() will return a location based on the application's location permissions. In this case the application has permission for the most accurate location possible:

(bad code)

Example Language: Java 

locationClient = new LocationClient(this, this, this);
locationClient.connect();
Location userCurrLocation;
userCurrLocation = locationClient.getLastLocation();
deriveStateFromCoords(userCurrLocation);

While the application needs this information, it does not need to use the ACCESS_FINE_LOCATION permission, as the ACCESS_COARSE_LOCATION permission will be sufficient to identify which US state the user is in.

Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Rust library leaks Oauth client details in application debug logs

Digital Rights Management (DRM) capability for mobile platform leaks pointer information, simplifying ASLR bypass

Enumeration of valid usernames based on inconsistent responses

Account number enumeration via inconsistent responses.

User enumeration via discrepancies in error messages.

Telnet protocol allows servers to obtain sensitive environment information from clients.

Script calls phpinfo(), revealing system configuration to web user

Product sets a different TTL when a port is being filtered than when it is not being filtered, which allows remote attackers to identify filtered ports by comparing TTLs.

Version control system allows remote attackers to determine the existence of arbitrary files and directories via the -X command for an alternate history file, which causes different error messages to be returned.

Virtual machine allows malicious web site operators to determine the existence of files on the client by measuring delays in the execution of the getSystemResource method.

Product immediately sends an error message when a user does not exist, which allows remote attackers to determine valid usernames via a timing attack.

POP3 server reveals a password in an error message after multiple APOP commands are sent. Might be resultant from another weakness.

Program reveals password in error message if attacker can trigger certain database errors.

Composite: application running with high privileges (

) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (

).

Direct request to library file in web application triggers pathname leak in error message.

Malformed regexp syntax leads to information exposure in error message.

Password exposed in debug information.

FTP client with debug option enabled shows password to the screen.

Collaboration platform does not clear team emails in a response, allowing leak of email addresses

Weakness Ordinalities

Primary

(where the weakness exists independent of other weaknesses)

Developers may insert sensitive information that they do not believe, or they might forget to remove the sensitive information after it has been processed

Resultant

(where the weakness is typically related to the presence of some other weaknesses)

Separate mistakes or weaknesses could inadvertently make the sensitive information available to an attacker, such as in a detailed error message that can be read by an unauthorized party

Detection Methods

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

• Bytecode Weakness Analysis - including disassembler + source code weakness analysis
• Inter-application Flow Analysis

Effectiveness: SOAR Partial

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

• Web Application Scanner
• Web Services Scanner
• Database Scanners

Effectiveness: High

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

• Fuzz Tester
• Framework-based Fuzzer
• Automated Monitored Execution
• Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

• Manual Source Code Review (not inspections)

Effectiveness: High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

• Context-configured Source Code Weakness Analyzer

Cost effective for partial coverage:

• Source code Weakness Analyzer

Effectiveness: High

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

• Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

• Attack Modeling
• Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: High

Memberships

Vulnerability Mapping Notes

(this CWE ID should not be used to map to real-world vulnerabilities)

Rationale

Comments

Notes

Maintenance

As a result of mapping analysis in the 2020 Top 25 and more recent versions, this weakness is under review, since it is frequently misused in mapping to cover many problems that lead to loss of confidentiality. See Mapping Notes, Extended Description, and Alternate Terms.

Taxonomy Mappings

References

Content History

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