Generation of Error Message Containing Sensitive Information
Draft Base
Structure: Simple
Description
The product generates an error message that includes sensitive information about its environment, users, or associated data.
Common Consequences 1
Scope: Confidentiality
Impact: Read Application Data
Often this will either reveal sensitive information which may be used to launch another, more focused attack or disclose private information stored in the server. For example, an attempt to exploit a path traversal weakness (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) might yield the full pathname of the installed application. In turn, this could be used to select the proper number of ".." sequences to navigate to the targeted file. An attack using SQL injection (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) might not initially succeed, but an error message could reveal the malformed query, which would expose query logic and possibly even passwords or other sensitive information used within the query.
Detection Methods 5
Manual AnalysisHigh
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.Automated AnalysisModerate
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.Automated Dynamic AnalysisModerate
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.
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.)Potential Mitigations 7
Phase: 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.
Phase: Implementation
Handle exceptions internally and do not display errors containing potentially sensitive information to a user.
Phase: Implementation
Strategy: 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
Phase: ImplementationBuild and Compilation
Strategy: Compilation or Build Hardening
Debugging information should not make its way into a production release.
Phase: ImplementationBuild and Compilation
Strategy: Environment Hardening
Debugging information should not make its way into a production release.
Phase: 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.
Phase: System Configuration
Create default error pages or messages that do not leak any information.
Demonstrative Examples 4
In the following example, sensitive information might be printed depending on the exception that occurs.
Code Example:
Bad
Java
javaIf 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.
ID : DX-118
This code tries to open a database connection, and prints any exceptions that occur.Code Example:
Bad
PHP
php//print exception message that includes exception message and configuration file location* catch (Exception $e) { ``` echo 'Caught exception: ', $e->getMessage(), '\n'; echo 'Check credentials in config file at: ', $Mysql_config_location, '\n'; }
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.
Code Example:
Bad
Perl
perlavoid CWE-22, CWE-78, others.*
perlIf 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.
ID : DX-119
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.Code Example:
Bad
Java
javaThe 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 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) to directly access the database.
Observed Examples 9
CVE-2008-2049POP3 server reveals a password in an error message after multiple APOP commands are sent. Might be resultant from another weakness.
CVE-2007-5172Program reveals password in error message if attacker can trigger certain database errors.
CVE-2008-4638Composite: application running with high privileges (Execution with Unnecessary Privileges) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (Generation of Error Message Containing Sensitive Information).
CVE-2008-1579Existence of user names can be determined by requesting a nonexistent blog and reading the error message.
CVE-2007-1409Direct request to library file in web application triggers pathname leak in error message.
CVE-2008-3060Malformed input to login page causes leak of full path when IMAP call fails.
CVE-2005-0603Malformed regexp syntax leads to information exposure in error message.
CVE-2017-9615verbose logging stores admin credentials in a world-readablelog file
CVE-2018-1999036SSH password for private key stored in build log
References 8
Information Leakage
Web Application Security Consortium
ID: REF-174
Secure Programming with Static Analysis
Brian Chess and Jacob West
Addison-Wesley
2007
ID: REF-175
Writing Secure Code
Michael Howard and David LeBlanc
Microsoft Press
13-11-2001
ID: REF-176
24 Deadly Sins of Software Security
Michael Howard, David LeBlanc, and John Viega
McGraw-Hill
2010
ID: REF-44
24 Deadly Sins of Software Security
Michael Howard, David LeBlanc, and John Viega
McGraw-Hill
2010
ID: REF-44
Top 25 Series - Rank 16 - Information Exposure Through an Error Message
Johannes Ullrich
SANS Software Security Institute
17-03-2010
ID: REF-179
The Art of Software Security Assessment
Mark Dowd, John McDonald, and Justin Schuh
Addison Wesley
2006
ID: REF-62
The CLASP Application Security Process
Secure Software, Inc.
2005
ID: REF-18
Likelihood of Exploit
High
Applicable Platforms
Languages:
PHP : OftenJava : OftenNot Language-Specific : Undetermined
Modes of Introduction
Architecture and Design
Implementation
System Configuration
Operation
Related Weaknesses
Taxonomy Mapping
- CLASP
- OWASP Top Ten 2007
- OWASP Top Ten 2004
- OWASP Top Ten 2004
- The CERT Oracle Secure Coding Standard for Java (2011)
- Software Fault Patterns
Notes
Other
The sensitive information may be valuable information on its own (such as a password), or it may be useful for launching other, more serious attacks.
The error message may be created in different ways:
- self-generated: the source code explicitly constructs the error message and delivers it
- externally-generated: the external environment, such as a language interpreter, handles the error and constructs its own message, whose contents are not under direct control by the programmer