The software 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. 1000 Weakness ChildOf 706 699 Category ChildOf 171 1000 Weakness CanPrecede 433 1000 Weakness CanPrecede 289 631 Category ChildOf 632 888 Category ChildOf 896 Implementation Access_Control Bypass protection mechanism Architecture and Design Input Validation Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names. Implementation Input Validation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist 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 (i.e., do not rely on a blacklist). A blacklist 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, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. Implementation 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 whitelist validation schemes by introducing dangerous inputs after they have been checked. In the following example, an XSS neutralization method replaces script tags in user supplied input with a safe equivalent: 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 blacklist (CWE-184). Equivalent tags such as "SCRIPT" or "ScRiPt" will not be neutralized by this method, allowing an XSS attack. 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. 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". 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". 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. 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. 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. 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". CVE-2002-0485 Leads to interpretation error CVE-1999-0239 Directories may be listed because lower case web requests are not properly handled by the server. 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. 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. CVE-2002-2119 Case insensitive passwords lead to search space reduction. CVE-2004-2214 HTTP server allows bypass of access restrictions using URIs with mixed case. CVE-2004-2154 Mixed upper/lowercase allows bypass of ACLs. CVE-2005-4509 Bypass malicious script detection by using tokens that aren't case sensitive. CVE-2002-1820 Mixed case problem allows "admin" to have "Admin" rights (alternate name property). CVE-2007-3365 Chain: uppercase file extensions causes web server to return script source code instead of executing the script. File Processing, Credentials File/Directory 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. Case Sensitivity (lowercase, uppercase, mixed case) PLOVER Sean Eidemiller Cigital 2008-07-01 added/updated demonstrative examples Eric Dalci Cigital 2008-07-01 updated Potential_Mitigations, Time_of_Introduction CWE Content Team MITRE 2008-09-08 updated Description, Relationships, Observed_Example, Taxonomy_Mappings CWE Content Team MITRE 2008-10-14 updated Observed_Examples CWE Content Team MITRE 2008-11-24 updated Observed_Examples CWE Content Team MITRE 2009-03-10 updated Description CWE Content Team MITRE 2009-07-27 updated Potential_Mitigations CWE Content Team MITRE 2010-06-21 updated Demonstrative_Examples CWE Content Team MITRE 2010-12-13 updated Name CWE Content Team MITRE 2011-03-29 updated Potential_Mitigations CWE Content Team MITRE 2011-06-01 updated Common_Consequences CWE Content Team MITRE 2012-05-11 updated Observed_Examples, Relationships CWE Content Team MITRE 2012-10-30 updated Demonstrative_Examples, Potential_Mitigations Case Sensitivity (Lowercase, Uppercase, Mixed Case) Failure to Resolve Case Sensitivity