Base weakness

Draft

CWE-209: Generation of Error Message Containing Sensitive Information

The product generates an error message that includes sensitive information about its environment, users, or associated data.

348

Recorded CVEs

With this primary weakness

KEVs

In the CISA KEV catalog

High

Likelihood of exploit

Per MITRE

Base

Abstraction

MITRE classification

Overview

CWE-209 (Generation of Error Message Containing Sensitive Information) is a base-level software weakness catalogued by MITRE in the Common Weakness Enumeration (CWE). It describes a recurring type of mistake that can lead to exploitable security vulnerabilities.

Real-world CVEs

How to prevent it

Practical mitigations for CWE-209, grouped by where in the lifecycle they apply.

Implementation

Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.

If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.

Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.

Implementation

Handle exceptions internally and do not display errors containing potentially sensitive information to a user.

Implementation

Attack Surface Reduction

Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

Effectiveness: Defense in Depth — This makes it easier to spot places in the code where data is being used that is unencrypted.

Implementation

Build and Compilation

Compilation or Build Hardening

Debugging information should not make its way into a production release.

Implementation

Build and Compilation

Environment Hardening

Debugging information should not make its way into a production release.

System Configuration

Where available, configure the environment to use less verbose error messages. For example, in PHP, disable the display_errors setting during configuration, or at runtime using the error_reporting() function.

System Configuration

Create default error pages or messages that do not leak any information.

How to detect it

Manual Analysis

This weakness generally requires domain-specific interpretation using manual analysis. However, the number of potential error conditions may be too large to cover completely within limited time constraints.

Effectiveness: High

Automated Analysis

Automated methods may be able to detect certain idioms automatically, such as exposed stack traces or pathnames, but violation of business rules or privacy requirements is not typically feasible.

Effectiveness: Moderate

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Error conditions may be triggered with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior.

Effectiveness: Moderate

Manual Dynamic Analysis

Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still indicate unexpected conditions that were not handled by the application itself.

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

In the following example, sensitive information might be printed depending on the exception that occurs.

Vulnerable example

java

try {

If an exception related to SQL is handled by the catch, then the output might contain sensitive information such as SQL query structure or private information. If this output is redirected to a web user, this may represent a security problem.

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

Vulnerable example

php

//print exception message that includes exception message and configuration file location
try {

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.

The following code generates an error message that leaks the full pathname of the configuration file.

Vulnerable example

perl

# avoid CWE-22, CWE-78, others.
$ConfigDir = "/home/myprog/config";

If this code is running on a server, such as a web application, then the person making the request should not know what the full pathname of the configuration directory is. By submitting a username that does not produce a $file that exists, an attacker could get this pathname. It could then be used to exploit path traversal or symbolic link following problems that may exist elsewhere in the application.

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.

Vulnerable example

java

public BankAccount getUserBankAccount(String username, String accountNumber) {

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.

CWE-209: Generation of Error Message Containing Sensitive Information

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Manual Analysis

Automated Analysis

Automated Dynamic Analysis

Manual Dynamic Analysis

Automated Static Analysis

Code examples

Illustrative examples

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-209?

What CVEs are caused by CWE-209?

Is CWE-209 part of the OWASP Top 10?

How do you prevent CWE-209?

How is CWE-209 detected?

What are the consequences of CWE-209?

Is CWE-209 actively exploited?

References

Stay ahead of CWE-209

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Manual Analysis

Automated Analysis

Automated Dynamic Analysis

Manual Dynamic Analysis

Automated Static Analysis

Code examples

Illustrative examples

Related weaknesses

Parent

Child

Peer

Related

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-209?

What CVEs are caused by CWE-209?

Is CWE-209 part of the OWASP Top 10?

How do you prevent CWE-209?

How is CWE-209 detected?

What are the consequences of CWE-209?

Is CWE-209 actively exploited?

References

Stay ahead of CWE-209