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CWE-537 Variant Incomplete
Java Runtime Error Message Containing Sensitive Information
This vulnerability occurs when a Java application's runtime error messages reveal sensitive details about the system, such as file paths, internal IP addresses, or stack traces. Attackers can…
Definition
What is CWE-537?
This vulnerability occurs when a Java application's runtime error messages reveal sensitive details about the system, such as file paths, internal IP addresses, or stack traces. Attackers can exploit these overly informative error messages to map the application's structure and gather intelligence for further attacks.
When an unhandled exception occurs, the default behavior in many Java applications is to display a detailed error message to the user. These messages often contain internal data like server file system paths, database connection strings, library versions, or configuration details. This information is invaluable to an attacker, as it helps them understand the underlying technology stack and pinpoint weaknesses without needing to probe the system directly.
To prevent this, developers should implement a global exception handler that catches all unhandled exceptions and replaces verbose system-generated messages with generic, user-friendly ones. All detailed error information should be logged securely on the server side for debugging purposes, never exposed to the end-user. This practice, often called 'security through obscurity,' is a critical layer in a defense-in-depth strategy, ensuring that failures don't inadvertently hand attackers a roadmap to your system.
Real-world impact
Real-world CVEs caused by CWE-537
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 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.
- 2
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.
- 3
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.
- 4
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.
Vulnerable code example
Vulnerable Java
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) {...}
}
} Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-537
- Implementation Do not expose sensitive error information to the user.
Detection signals
How to detect CWE-537
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
Plexicus auto-detects CWE-537 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-537?
How serious is CWE-537?
What languages or platforms are affected by CWE-537?
How can I prevent CWE-537?
How does Plexicus detect and fix CWE-537?
Where can I learn more about CWE-537?
Frequently asked questions
What is CWE-537?
This vulnerability occurs when a Java application's runtime error messages reveal sensitive details about the system, such as file paths, internal IP addresses, or stack traces. Attackers can exploit these overly informative error messages to map the application's structure and gather intelligence for further attacks.
How serious is CWE-537?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-537?
MITRE lists the following affected platforms: Java.
How can I prevent CWE-537?
Do not expose sensitive error information to the user.
How does Plexicus detect and fix CWE-537?
Plexicus's SAST engine matches the data-flow signature for CWE-537 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-537?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/537.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-537
CWE-211 Parent
Externally-Generated Error Message Containing Sensitive Information
This vulnerability occurs when an application triggers an error message from an external component—like a database, interpreter, or…
CWE-535 Sibling
Exposure of Information Through Shell Error Message
This vulnerability occurs when a web application's command shell returns detailed error messages to users. Attackers can analyze these…
CWE-536 Sibling
Servlet Runtime Error Message Containing Sensitive Information
This vulnerability occurs when a Java servlet application displays detailed runtime error messages that reveal sensitive information about…
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