In many cases, an attacker can leverage the conditions that cause unhandled exception errors in order to gain unauthorized access to the system.

Resultant

Implementation

Confidentiality
Read Application Data

Implementation
Do not expose sensitive error information to the user.

In the following Java example the class InputFileRead enables an input file to be read using a FileReader object. In the constructor of this class a default input file path is set to some directory on the local file system and the method setInputFile must be called to set the name of the input file to be read in the default directory. The method readInputFile will create the FileReader object and will read the contents of the file. If the method setInputFile is not called prior to calling the method readInputFile then the File object will remain null when initializing the FileReader object. A Java RuntimeException will be raised, and an error message will be output to the user.

public class InputFileRead {

private File readFile = null;private FileReader reader = null;private String inputFilePath = null;private final String DEFAULT_FILE_PATH = "c:\\somedirectory\\";
public InputFileRead() {inputFilePath = DEFAULT_FILE_PATH;}
public void setInputFile(String inputFile) {

/* Assume appropriate validation / encoding is used and privileges / permissions are preserved */

}
public void readInputFile() {
try {reader = new FileReader(readFile);...} catch (RuntimeException rex) {System.err.println("Error: Cannot open input file in the directory " + inputFilePath);System.err.println("Input file has not been set, call setInputFile method before calling readInputFile");

} catch (FileNotFoundException ex) {...}

}
}

However, the error message output to the user contains information regarding the default directory on the local file system. This information can be exploited and may lead to unauthorized access or use of the system. Any Java RuntimeExceptions that are handled should not expose sensitive information to the user.

In the example below, the BankManagerLoginServlet servlet class will process a login request to determine if a user is authorized to use the BankManager Web service. The doPost method will retrieve the username and password from the servlet request and will determine if the user is authorized. If the user is authorized the servlet will go to the successful login page. Otherwise, the servlet will raise a FailedLoginException and output the failed login message to the error page of the service.

public class BankManagerLoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {

// Get username and password from login page request
String username = request.getParameter("username");String password = request.getParameter("password");
// Authenticate user
BankManager bankMgr = new BankManager();boolean isAuthentic = bankMgr.authenticateUser(username, password);
// If user is authenticated then go to successful login page
if (isAuthentic) {request.setAttribute("login", new String("Login Successful."));getServletContext().getRequestDispatcher("/BankManagerServiceLoggedIn.jsp"). forward(request, response);}else {

// Otherwise, raise failed login exception and output unsuccessful login message to error page
throw new FailedLoginException("Failed Login for user " + username + " with password " + password);
}
} catch (FailedLoginException ex) {

// output failed login message to error page
request.setAttribute("error", new String("Login Error"));request.setAttribute("message", ex.getMessage());getServletContext().getRequestDispatcher("/ErrorPage.jsp").forward(request, response);
}
}

However, the output message generated by the FailedLoginException includes the user-supplied password. Even if the password is erroneous, it is probably close to the correct password. Since it is printed to the user's page, anybody who can see the screen display will be able to see the password. Also, if the page is cached, the password might be written to disk.

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Anonymous Tool Vendor (under NDA)
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Potential_Mitigations, Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2010-02-16
updated Demonstrative_Examples, Potential_Mitigations

CWE Content Team
MITRE
2011-03-29
updated Demonstrative_Examples, Name

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2014-07-30
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated Name, Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-04-27
updated Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2024-02-29
4.14
2024-02-29
updated Demonstrative_Examples

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Weakness_Ordinalities

Information Leak Through Java Runtime Error Message
Information Exposure Through Java Runtime Error Message