CWE-497: Exposure of Sensitive System Information to an Unauthorized Control Sphere

Description

The product does not properly prevent sensitive system-level information from being accessed by unauthorized actors who do not have the same level of access to the underlying system as the product does.

Network-based products, such as web applications, often run on top of an operating system or similar environment. When the product communicates with outside parties, details about the underlying system are expected to remain hidden, such as path names for data files, other OS users, installed packages, the application environment, etc. This system information may be provided by the product itself, or buried within diagnostic or debugging messages. Debugging information helps an adversary learn about the system and form an attack plan. An information exposure occurs when system data or debugging information leaves the program through an output stream or logging function that makes it accessible to unauthorized parties. Using other weaknesses, an attacker could cause errors to occur; the response to these errors can reveal detailed system information, along with other impacts. An attacker can use messages that reveal technologies, operating systems, and product versions to tune the attack against known vulnerabilities in these technologies. A product may use diagnostic methods that provide significant implementation details such as stack traces as part of its error handling mechanism.

Potential Impact

Confidentiality

Read Application Data

Demonstrative Examples

The following code prints the path environment variable to the standard error stream:

Bad

char* path = getenv("PATH");...sprintf(stderr, "cannot find exe on path %s\n", path);

This code prints all of the running processes belonging to the current user.

Bad

//assume getCurrentUser() returns a username that is guaranteed to be alphanumeric (avoiding CWE-78)
                     $userName = getCurrentUser();$command = 'ps aux | grep ' . $userName;system($command);

If invoked by an unauthorized web user, it is providing a web page of potentially sensitive information on the underlying system, such as command-line arguments (CWE-497). This program is also potentially vulnerable to a PATH based attack (CWE-426), as an attacker may be able to create malicious versions of the ps or grep commands. While the program does not explicitly raise privileges to run the system commands, the PHP interpreter may by default be running with higher privileges than users.

The following code prints an exception to the standard error stream:

Bad

try {...} catch (Exception e) {e.printStackTrace();}

Bad

try {...} catch (Exception e) {Console.Writeline(e);}

Depending upon the system configuration, this information can be dumped to a console, written to a log file, or exposed to a remote user. In some cases the error message tells the attacker precisely what sort of an attack the system will be vulnerable to. For example, a database error message can reveal that the application is vulnerable to a SQL injection attack. Other error messages can reveal more oblique clues about the system. In the example above, the search path could imply information about the type of operating system, the applications installed on the system, and the amount of care that the administrators have put into configuring the program.

The following code constructs a database connection string, uses it to create a new connection to the database, and prints it to the console.

Bad

string cs="database=northwind; server=mySQLServer...";SqlConnection conn=new SqlConnection(cs);...Console.Writeline(cs);

Depending on the system configuration, this information can be dumped to a console, written to a log file, or exposed to a remote user. In some cases the error message tells the attacker precisely what sort of an attack the system is vulnerable to. For example, a database error message can reveal that the application is vulnerable to a SQL injection attack. Other error messages can reveal more oblique clues about the system. In the example above, the search path could imply information about the type of operating system, the applications installed on the system, and the amount of care that the administrators have put into configuring the program.

Mitigations & Prevention

Architecture and DesignImplementation

Production applications should never use methods that generate internal details such as stack traces and error messages unless that information is directly committed to a log that is not viewable by the end user. All error message text should be HTML entity encoded before being written to the log file to protect against potential cross-site scripting attacks against the viewer of the logs

Detection Methods

Automated Static Analysis High — 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 sea

Real-World CVE Examples

CVE ID	Description
CVE-2021-32638	Code analysis product passes access tokens as a command-line parameter or through an environment variable, making them visible to other processes via the ps command.

Taxonomy Mappings

7 Pernicious Kingdoms: — System Information Leak
The CERT Oracle Secure Coding Standard for Java (2011): ERR01-J — Do not allow exceptions to expose sensitive information
Software Fault Patterns: SFP23 — Exposed Data

Frequently Asked Questions

What is CWE-497?

CWE-497 (Exposure of Sensitive System Information to an Unauthorized Control Sphere) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product does not properly prevent sensitive system-level information from being accessed by unauthorized actors who do not have the same level of access to the underlying system as the product doe...

How can CWE-497 be exploited?

Attackers can exploit CWE-497 (Exposure of Sensitive System Information to an Unauthorized Control Sphere) to read application data. This weakness is typically introduced during the Implementation phase of software development.

How do I prevent CWE-497?

Key mitigations include: Production applications should never use methods that generate internal details such as stack traces and error messages unless that information is directly committed to a log that is not viewable by t

What is the severity of CWE-497?

CWE-497 is classified as a Base-level weakness (Medium abstraction). It has been observed in 1 real-world CVEs.