CWE-12: ASP.NET Misconfiguration: Missing Custom Error Page

Code Examples & CVEs

Demonstrative Examples

The mode attribute of the <customErrors> tag in the Web.config file defines whether custom or default error pages are used.

In the following insecure ASP.NET application setting, custom error message mode is turned off. An ASP.NET error message with detailed stack trace and platform versions will be returned.

BadASP.NET

<customErrors mode="Off" />

The mode attribute of the <customErrors> tag in the Web.config file defines whether custom or default error pages are used.

In the following insecure ASP.NET application setting, custom error message mode is turned off. An ASP.NET error message with detailed stack trace and platform versions will be returned.

GoodASP.NET

<customErrors mode="RemoteOnly" />

The mode attribute of the <customErrors> tag in the Web.config file defines whether custom or default error pages are used.

In the following insecure ASP.NET application setting, custom error message mode is turned off. An ASP.NET error message with detailed stack trace and platform versions will be returned.

GoodASP.NET

<customErrors mode="On" defaultRedirect="YourErrorPage.htm" />

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-12 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-12, ASP.NET Misconfiguration: Missing Custom Error Page, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address ASP.NET Misconfiguration: Missing Custom Error Page during System Configuration

MITRE associates mitigation with System Configuration, Architecture and Design, and Implementation; recorded impacts include Read Application Data; related weaknesses include CWE-756. Use these source-defined anchors to turn CWE-12 into implementation, review, and verification checks for the affected component.

CWE-12: ASP.NET Misconfiguration: Missing Custom Error Page — MITRE CWE

Triage CWE-12 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-12, ASP.NET Misconfiguration: Missing Custom Error Page, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-12

Apply MITRE's full root-cause mapping guidance when using CWE-12, ASP.NET Misconfiguration: Missing Custom Error Page. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-12 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-12, ASP.NET Misconfiguration: Missing Custom Error Page. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-12: ASP.NET Misconfiguration: Missing Custom Error Page?+

CWE-12: ASP.NET Misconfiguration: Missing Custom Error Page is a Common Weakness Enumeration (CWE) entry maintained by MITRE. An ASP .NET application must enable custom error pages in order to prevent attackers from mining information from the framework's built-in responses.

What are the security consequences of ASP.NET Misconfiguration: Missing Custom Error Page?+

If exploited, CWE-12 (ASP.NET Misconfiguration: Missing Custom Error Page) it can compromise Confidentiality, leading to outcomes such as Read Application Data.

How do you prevent or mitigate ASP.NET Misconfiguration: Missing Custom Error Page?+

Recommended mitigations for CWE-12 include: Handle exceptions appropriately in source code. ASP .NET applications should be configured to use custom error pages instead of the framework default page. Do not attempt to process an error or attempt to mask it. Verify return values are correct and do not supply sensitive information about the system.

Which programming languages are affected by ASP.NET Misconfiguration: Missing Custom Error Page?+

CWE-12 commonly affects ASP.NET. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-12 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-12: ASP.NET Misconfiguration: Missing Custom Error Page

Technical Details

Applicable To

Security Consequences

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Impact

Mitigation Strategies

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Description

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Detection Methods

Code Examples & CVEs

Demonstrative Examples

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-12 with SSDF evidence

Address ASP.NET Misconfiguration: Missing Custom Error Page during System Configuration

Triage CWE-12 against known exploitation evidence

Apply precise root-cause mapping to CWE-12

Validate CWE-12 with root-cause mapping checks

Frequently Asked Questions

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