CWE-178: Improper Handling of Case Sensitivity

Extended Description

Improperly handled case sensitive data can lead to several possible consequences, including: case-insensitive passwords reducing the size of the key space, making brute force attacks easier bypassing filters or access controls using alternate names multiple interpretation errors using alternate names.

Code Examples & CVEs

Demonstrative Examples

In the following example, an XSS neutralization method intends to replace script tags in user-supplied input with a safe equivalent:

The code only works when the "script" tag is in all lower-case, forming an incomplete denylist (CWE-184). Equivalent tags such as "SCRIPT" or "ScRiPt" will not be neutralized by this method, allowing an XSS attack.

BadJava

public String preventXSS(String input, String mask) {return input.replaceAll("script", mask);}

Observed CVE Examples (18)

CVE-2000-0499

Application server allows attackers to bypass execution of a jsp page and read the source code using an upper case JSP extension in the request.

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CVE-2000-0497

The server is case sensitive, so filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".

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CVE-2000-0498

The server is case sensitive, so filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".

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CVE-2001-0766

A URL that contains some characters whose case is not matched by the server's filters may bypass access restrictions because the case-insensitive file system will then handle the request after it bypasses the case sensitive filter.

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CVE-2001-0795

Server allows remote attackers to obtain source code of CGI scripts via URLs that contain MS-DOS conventions such as (1) upper case letters or (2) 8.3 file names.

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CVE-2001-1238

Task Manager does not allow local users to end processes with uppercase letters named (1) winlogon.exe, (2) csrss.exe, (3) smss.exe and (4) services.exe via the Process tab which could allow local users to install Trojan horses that cannot be stopped.

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CVE-2003-0411

chain: Code was ported from a case-sensitive Unix platform to a case-insensitive Windows platform where filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".

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CVE-2002-0485

Leads to interpretation error

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CVE-1999-0239

Directories may be listed because lower case web requests are not properly handled by the server.

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CVE-2005-0269

File extension check in forum software only verifies extensions that contain all lowercase letters, which allows remote attackers to upload arbitrary files via file extensions that include uppercase letters.

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CVE-2004-1083

Web server restricts access to files in a case sensitive manner, but the filesystem accesses files in a case insensitive manner, which allows remote attackers to read privileged files using alternate capitalization.

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CVE-2002-2119

Case insensitive passwords lead to search space reduction.

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CVE-2004-2214

HTTP server allows bypass of access restrictions using URIs with mixed case.

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CVE-2004-2154

Mixed upper/lowercase allows bypass of ACLs.

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CVE-2005-4509

Bypass malicious script detection by using tokens that aren't case sensitive.

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CVE-2002-1820

Mixed case problem allows "admin" to have "Admin" rights (alternate name property).

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CVE-2007-3365

Chain: uppercase file extensions causes web server to return script source code instead of executing the script.

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CVE-2021-39155

Chain: A microservice integration and management platform compares the hostname in the HTTP Host header in a case-sensitive way (CWE-178, CWE-1289), allowing bypass of the authorization policy (CWE-863) using a hostname with mixed case or other variations.

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Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-178 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-178, Improper Handling of Case Sensitivity, 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

Apply Input Validation controls for Improper Handling of Case Sensitivity

MITRE associates mitigation with Architecture and Design, and Implementation; the listed strategies include Input Validation; recorded impacts include Bypass Protection Mechanism. Use these source-defined anchors to turn CWE-178 into implementation, review, and verification checks for the affected component.

CWE-178: Improper Handling of Case Sensitivity — MITRE CWE

Triage CWE-178 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-178, Improper Handling of Case Sensitivity, 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-178

Apply MITRE's full root-cause mapping guidance when using CWE-178, Improper Handling of Case Sensitivity. 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-178 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-178, Improper Handling of Case Sensitivity. 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-178: Improper Handling of Case Sensitivity?+

CWE-178: Improper Handling of Case Sensitivity is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results. Improperly handled case sensitive data can lead to several possible consequences, including: case-insensitive passwords reducing the size of the key space, making brute force attacks easier bypassing filters or access controls using alternate names multiple interpretation errors using alternate names.

What are the security consequences of Improper Handling of Case Sensitivity?+

If exploited, CWE-178 (Improper Handling of Case Sensitivity) it can compromise Access Control, leading to outcomes such as Bypass Protection Mechanism.

Which programming languages are affected by Improper Handling of Case Sensitivity?+

CWE-178 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Improper Handling of Case Sensitivity?+

MITRE documents real CVEs mapped to CWE-178, including CVE-2000-0499, CVE-2000-0497, CVE-2000-0498, CVE-2001-0766 and CVE-2001-0795. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

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

A CWE (Common Weakness Enumeration) like CWE-178 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-178: Improper Handling of Case Sensitivity

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (18)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-178 with SSDF evidence

Apply Input Validation controls for Improper Handling of Case Sensitivity

Triage CWE-178 against known exploitation evidence

Apply precise root-cause mapping to CWE-178

Validate CWE-178 with root-cause mapping checks

Frequently Asked Questions

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