CA3004: Review code for information disclosure vulnerabilities

Property	Value
Rule ID	CA3004
Title	Review code for information disclosure vulnerabilities
Category	Security
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 9	No

Cause

An exception's message, stack trace, or string representation reaches web output.

By default, this rule analyzes the entire codebase, but this is configurable.

Rule description

Disclosing exception information gives attackers insight into the internals of your application, which can help attackers find other vulnerabilities to exploit.

This rule attempts to find an exception message, stack trace, or string representation being output to an HTTP response.

Note

This rule can't track data across assemblies. For example, if one assembly catches an exception and then passes it to another assembly that outputs the exception, this rule won't produce a warning.

Note

There is a configurable limit to how deep this rule will analyze data flow across method calls. For information about how to configure the limit in an EditorConfig file, see Analyzer Configuration.

How to fix violations

Don't output exception information to HTTP responses. Instead, provide a generic error message. For more information, see OWASP's Improper Error Handling page.

When to suppress warnings

If you know your web output is within your application's trust boundary and never exposed outside, it's okay to suppress this warning. This is rare. Take into consideration that your application's trust boundary and data flows may change over time.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

C#

#pragma warning disable CA3004
// The code that's violating the rule is on this line.
#pragma warning restore CA3004

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

ini

[*.{cs,vb}]
dotnet_diagnostic.CA3004.severity = none

For more information, see How to suppress code analysis warnings.

Configure code to analyze

Use the following options to configure which parts of your codebase to run this rule on.

• Exclude specific symbols
• Exclude specific types and their derived types

You can configure these options for just this rule, for all rules they apply to, or for all rules in this category (Security) that they apply to. For more information, see Code quality rule configuration options.

Exclude specific symbols

You can exclude specific symbols, such as types and methods, from analysis by setting the excluded_symbol_names option. For example, to specify that the rule should not run on any code within types named MyType, add the following key-value pair to an .editorconfig file in your project:

ini

dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType

Note

Replace the XXXX part of CAXXXX with the ID of the applicable rule.

Allowed symbol name formats in the option value (separated by |):

• Symbol name only (includes all symbols with the name, regardless of the containing type or namespace).
• Fully qualified names in the symbol's documentation ID format. Each symbol name requires a symbol-kind prefix, such as M: for methods, T: for types, and N: for namespaces.
• .ctor for constructors and .cctor for static constructors.

Examples:

Option Value	Summary
dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType	Matches all symbols named MyType.
dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType1|MyType2	Matches all symbols named either MyType1 or MyType2.
dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS.MyType.MyMethod(ParamType)	Matches specific method MyMethod with the specified fully qualified signature.
dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS1.MyType1.MyMethod1(ParamType)|M:NS2.MyType2.MyMethod2(ParamType)	Matches specific methods MyMethod1 and MyMethod2 with the respective fully qualified signatures.

Exclude specific types and their derived types

You can exclude specific types and their derived types from analysis by setting the excluded_type_names_with_derived_types option. For example, to specify that the rule should not run on any methods within types named MyType and their derived types, add the following key-value pair to an .editorconfig file in your project:

ini

dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType

Note

Replace the XXXX part of CAXXXX with the ID of the applicable rule.

Allowed symbol name formats in the option value (separated by |):

• Type name only (includes all types with the name, regardless of the containing type or namespace).
• Fully qualified names in the symbol's documentation ID format, with an optional T: prefix.

Examples:

Option value	Summary
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType	Matches all types named MyType and all of their derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType1|MyType2	Matches all types named either MyType1 or MyType2 and all of their derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS.MyType	Matches specific type MyType with given fully qualified name and all of its derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS1.MyType1|M:NS2.MyType2	Matches specific types MyType1 and MyType2 with the respective fully qualified names, and all of their derived types.

Pseudo-code examples

Violation

C#

using System;

public partial class WebForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs eventArgs)
    {
        try
        {
            object o = null;
            o.ToString();
        }
        catch (Exception e)
        {
            this.Response.Write(e.ToString());
        }
    }
}

Solution

C#

using System;

public partial class WebForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs eventArgs)
    {
        try
        {
            object o = null;
            o.ToString();
        }
        catch (Exception e)
        {
            this.Response.Write("An error occurred. Please try again later.");
        }
    }
}