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CWE-537: Information Exposure Through Java Runtime Error Message

Weakness ID: 537
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

In many cases, an attacker can leverage the conditions that cause unhandled exception errors in order to gain unauthorized access to the system.
+ Time of Introduction
  • Implementation
+ Applicable Platforms



+ Common Consequences

Technical Impact: Read application data

+ Demonstrative Examples

Example 1

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.

(Bad Code)
Example Language: Java 
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.

Example 2

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.

(Bad Code)
Example Language: Java 
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.

+ Potential Mitigations

Phase: Implementation

Do not expose sensitive error information to the user.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base210Information Exposure Through Self-generated Error Message
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
+ Content History
Submission DateSubmitterOrganizationSource
Anonymous Tool Vendor (under NDA)Externally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2010-02-16CWE Content TeamMITREInternal
updated Demonstrative_Examples, Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Demonstrative_Examples, Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2011-03-29Information Leak Through Java Runtime Error Message

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Page Last Updated: May 05, 2017