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Home > CWE List > CWE-178: Improper Handling of Case Sensitivity (4.18)
ID
CWE Glossary Definition

CWE-178: Improper Handling of Case Sensitivity

Weakness ID: 178
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
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Description
The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
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.
Common Consequences
Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Impact Details

Bypass Protection Mechanism

Scope: Access Control

Potential Mitigations
Phase(s) Mitigation

Architecture and Design

Strategy: Input Validation

Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.

Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Relationships
Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (View-1000)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 706 Use of Incorrectly-Resolved Name or Reference
PeerOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 1289 Improper Validation of Unsafe Equivalence in Input
CanPrecede Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 289 Authentication Bypass by Alternate Name
CanPrecede Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 433 Unparsed Raw Web Content Delivery
Relevant to the view "Software Development" (View-699)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 19 Data Processing Errors
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 706 Use of Incorrectly-Resolved Name or Reference
Modes Of Introduction
Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase Note
Implementation
Applicable Platforms
Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages

Class: Not Language-Specific (Undetermined Prevalence)

Demonstrative Examples

Example 1


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

(bad code)
Example Language: Java
public String preventXSS(String input, String mask) {
return input.replaceAll("script", mask);
}

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.



Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
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.
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".
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".
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.
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.
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.
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".
Leads to interpretation error
Directories may be listed because lower case web requests are not properly handled by the server.
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.
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.
Case insensitive passwords lead to search space reduction.
HTTP server allows bypass of access restrictions using URIs with mixed case.
Mixed upper/lowercase allows bypass of ACLs.
Bypass malicious script detection by using tokens that aren't case sensitive.
Mixed case problem allows "admin" to have "Admin" rights (alternate name property).
Chain: uppercase file extensions causes web server to return script source code instead of executing the script.
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.
Functional Areas
  • File Processing
Affected Resources
  • File or Directory
Memberships
Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature Type ID Name
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 992 SFP Secondary Cluster: Faulty Input Transformation
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1416 Comprehensive Categorization: Resource Lifecycle Management
Vulnerability Mapping Notes
Usage ALLOWED
(this CWE ID may be used to map to real-world vulnerabilities)
Reason Acceptable-Use

Rationale

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
Notes

Research Gap

These are probably under-studied in Windows and Mac environments, where file names are case-insensitive and thus are subject to equivalence manipulations involving case.
Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Case Sensitivity (lowercase, uppercase, mixed case)
Content History
Submissions
Submission Date Submitter Organization
2006年07月19日
(CWE Draft 3, 2006年07月19日) 		PLOVER
Modifications
Modification Date Modifier Organization
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes
2023年04月27日 CWE Content Team MITRE
updated Relationships
2023年01月31日 CWE Content Team MITRE
updated Description
2022年10月13日 CWE Content Team MITRE
updated Observed_Examples
2021年03月15日 CWE Content Team MITRE
updated Demonstrative_Examples
2020年06月25日 CWE Content Team MITRE
updated Demonstrative_Examples, Potential_Mitigations, Relationships
2020年02月24日 CWE Content Team MITRE
updated Potential_Mitigations, Relationships
2019年06月20日 CWE Content Team MITRE
updated Relationships
2017年11月08日 CWE Content Team MITRE
updated Affected_Resources, Applicable_Platforms, Functional_Areas, Relationships
2014年07月30日 CWE Content Team MITRE
updated Relationships
2012年10月30日 CWE Content Team MITRE
updated Demonstrative_Examples, Potential_Mitigations
2012年05月11日 CWE Content Team MITRE
updated Observed_Examples, Relationships
2011年06月01日 CWE Content Team MITRE
updated Common_Consequences
2011年03月29日 CWE Content Team MITRE
updated Potential_Mitigations
2010年12月13日 CWE Content Team MITRE
updated Name
2010年06月21日 CWE Content Team MITRE
updated Demonstrative_Examples
2009年07月27日 CWE Content Team MITRE
updated Potential_Mitigations
2009年03月10日 CWE Content Team MITRE
updated Description
2008年11月24日 CWE Content Team MITRE
updated Observed_Examples
2008年10月14日 CWE Content Team MITRE
updated Observed_Examples
2008年09月08日 CWE Content Team MITRE
updated Description, Relationships, Observed_Example, Taxonomy_Mappings
2008年07月01日 Eric Dalci Cigital
updated Potential_Mitigations, Time_of_Introduction
2008年07月01日 Sean Eidemiller Cigital
added/updated demonstrative examples
Previous Entry Names
Change Date Previous Entry Name
2008年04月11日 Case Sensitivity (Lowercase, Uppercase, Mixed Case)
2010年12月13日 Failure to Resolve Case Sensitivity
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Page Last Updated: September 09, 2025

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