Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-7 Variant Incomplete
J2EE Misconfiguration: Missing Custom Error Page
This vulnerability occurs when a J2EE application uses the server's default error pages instead of custom ones, potentially leaking sensitive system details.
Definition
What is CWE-7?
This vulnerability occurs when a J2EE application uses the server's default error pages instead of custom ones, potentially leaking sensitive system details.
A secure web application must define custom error pages for all client-side (4xx) and server-side (5xx) errors, and also catch generic Throwable exceptions. This prevents the application container from sending its built-in error responses, which often include stack traces, server versions, and internal configuration details that attackers can use to map your system.
When attackers probe for weaknesses, the information your application reveals directly influences their success. By replacing default error pages with neutral, user-friendly messages, you remove a critical source of intelligence that could enable more targeted and damaging exploits.
Real-world impact
Real-world CVEs caused by CWE-7
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable Java
In the snippet below, an unchecked runtime exception thrown from within the try block may cause the container to display its default error page (which may contain a full stack trace, among other things).
Public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
...
} catch (ApplicationSpecificException ase) {
logger.error("Caught: " + ase.toString());
}
} 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-7
- Implementation Handle exceptions appropriately in source code.
- Implementation / System Configuration Always define appropriate error pages. The application configuration should specify a default error page in order to guarantee that the application will never leak error messages to an attacker. Handling standard HTTP error codes is useful and user-friendly in addition to being a good security practice, and a good configuration will also define a last-chance error handler that catches any exception that could possibly be thrown by the application.
- Implementation Do not attempt to process an error or attempt to mask it.
- Implementation Verify return values are correct and do not supply sensitive information about the system.
Detection signals
How to detect CWE-7
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.
CWE-7
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-7?
How serious is CWE-7?
What languages or platforms are affected by CWE-7?
How can I prevent CWE-7?
How does Plexicus detect and fix CWE-7?
Where can I learn more about CWE-7?
Frequently asked questions
What is CWE-7?
This vulnerability occurs when a J2EE application uses the server's default error pages instead of custom ones, potentially leaking sensitive system details.
How serious is CWE-7?
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-7?
MITRE lists the following affected platforms: Java.
How can I prevent CWE-7?
Handle exceptions appropriately in source code. Always define appropriate error pages. The application configuration should specify a default error page in order to guarantee that the application will never leak error messages to an attacker. Handling standard HTTP error codes is useful and user-friendly in addition to being a good security practice, and a good configuration will also define a last-chance error handler that catches any exception that could possibly be thrown by the application.
How does Plexicus detect and fix CWE-7?
Plexicus's SAST engine matches the data-flow signature for CWE-7 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-7?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/7.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-7
CWE-756 Parent
Missing Custom Error Page
This vulnerability occurs when an application fails to display its own user-friendly error pages, instead falling back to default system…
CWE-12 Sibling
ASP.NET Misconfiguration: Missing Custom Error Page
This vulnerability occurs when an ASP.NET application fails to configure custom error pages, allowing attackers to extract sensitive…
Resources
Further reading
- MITRE — official CWE-7 https://cwe.mitre.org/data/definitions/7.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
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