{"@ID": "179", "@Name": "Incorrect Behavior Order: Early Validation", "@Abstraction": "Base", "@Structure": "Simple", "@Status": "Incomplete", "Description": "The product validates input before applying protection mechanisms that modify the input, which could allow an attacker to bypass the validation via dangerous inputs that only arise after the modification.", "Extended_Description": "Product needs to validate data at the proper time, after data has been canonicalized and cleansed. Early validation is susceptible to various manipulations that result in dangerous inputs that are produced by canonicalization and cleansing.", "Related_Weaknesses": {"Related_Weakness": [{"@Nature": "ChildOf", "@CWE_ID": "20", "@View_ID": "1000"}, {"@Nature": "ChildOf", "@CWE_ID": "696", "@View_ID": "1000", "@Ordinal": "Primary"}]}, "Weakness_Ordinalities": {"Weakness_Ordinality": {"Ordinality": "Primary"}}, "Applicable_Platforms": {"Language": {"@Class": "Not Language-Specific", "@Prevalence": "Undetermined"}}, "Modes_Of_Introduction": {"Introduction": {"Phase": "Implementation", "Note": "Since early validation errors usually arise from improperly implemented defensive mechanisms, it is likely that these will be introduced more frequently as secure programming becomes implemented more widely."}}, "Common_Consequences": {"Consequence": {"Scope": ["Access Control", "Integrity"], "Impact": ["Bypass Protection Mechanism", "Execute Unauthorized Code or Commands"], "Note": "An attacker could include dangerous input that bypasses validation protection mechanisms which can be used to launch various attacks including injection attacks, execute arbitrary code or cause other unintended behavior."}}, "Potential_Mitigations": {"Mitigation": {"@Mitigation_ID": "MIT-20", "Phase": "Implementation", "Strategy": "Input Validation", "Description": "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."}}, "Demonstrative_Examples": {"Demonstrative_Example": [{"@Demonstrative_Example_ID": "DX-35", "Intro_Text": "The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string \"/safe_dir/\".", "Example_Code": [{"@Nature": "Bad", "@Language": "Java", "xhtml:div": {"xhtml:br": [null, null], "xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": null, "#text": "File f = new File(path);return f.getCanonicalPath();"}, "#text": "String path = getInputPath();if (path.startsWith(\"/safe_dir/\")){}"}}, {"@Nature": "Good", "@Language": "Java", "xhtml:div": {"xhtml:br": [null, null, null, null, null], "xhtml:div": {"@style": "margin-left:1em;", "#text": "return f.getCanonicalPath();"}, "#text": "String path = getInputPath();File f = new File(path);if (f.getCanonicalPath().startsWith(\"/safe_dir/\")){}"}}], "Body_Text": ["The problem with the above code is that the validation step occurs before canonicalization occurs. An attacker could provide an input path of \"/safe_dir/../\" that would pass the validation step. However, the canonicalization process sees the double dot as a traversal to the parent directory and hence when canonicized the path would become just \"/\".", "To avoid this problem, validation should occur after canonicalization takes place. In this case canonicalization occurs during the initialization of the File object. The code below fixes the issue."]}, {"@Demonstrative_Example_ID": "DX-36", "Intro_Text": "This script creates a subdirectory within a user directory and sets the user as the owner.", "Example_Code": {"@Nature": "Bad", "@Language": "PHP", "xhtml:div": {"xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": [null, null, null, null, null, null], "xhtml:div": {"@style": "margin-left:1em;", "xhtml:br": null, "#text": "echo 'Directory name contains invalid sequence';return;"}, "xhtml:i": "//filter out '~' because other scripts identify user directories by this prefix", "#text": "$userDir = '/users/'. $userName;if(strpos($dirName,'..') !== false){}\n                        \n                        $dirName = str_replace('~','',$dirName);$newDir = $userDir . $dirName;mkdir($newDir, 0700);chown($newDir,$userName);"}, "#text": "function createDir($userName,$dirName){}"}}, "Body_Text": "While the script attempts to screen for '..' sequences, an attacker can submit a directory path including \".~.\", which will then become \"..\" after the filtering step. This allows a Path Traversal (CWE-21) attack to occur."}]}, "Observed_Examples": {"Observed_Example": [{"Reference": "CVE-2002-0433", "Description": "List files in web server using \"*.ext\"", "Link": "https://www.cve.org/CVERecord?id=CVE-2002-0433"}, {"Reference": "CVE-2003-0332", "Description": "Product modifies the first two letters of a filename extension after performing a security check, which allows remote attackers to bypass authentication via a filename with a .ats extension instead of a .hts extension.", "Link": "https://www.cve.org/CVERecord?id=CVE-2003-0332"}, {"Reference": "CVE-2002-0802", "Description": "Database consumes an extra character when processing a character that cannot be converted, which could remove an escape character from the query and make the application subject to SQL injection attacks.", "Link": "https://www.cve.org/CVERecord?id=CVE-2002-0802"}, {"Reference": "CVE-2000-0191", "Description": "Overlaps \"fakechild/../realchild\"", "Link": "https://www.cve.org/CVERecord?id=CVE-2000-0191"}, {"Reference": "CVE-2004-2363", "Description": "Product checks URI for \"<\" and other literal characters, but does it before hex decoding the URI, so \"%3E\" and other sequences are allowed.", "Link": "https://www.cve.org/CVERecord?id=CVE-2004-2363"}, {"Reference": "CVE-2002-0934", "Description": "Directory traversal vulnerability allows remote attackers to read or modify arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a \"..\" sequence.", "Link": "https://www.cve.org/CVERecord?id=CVE-2002-0934"}, {"Reference": "CVE-2003-0282", "Description": "Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a \"..\" sequence.", "Link": "https://www.cve.org/CVERecord?id=CVE-2003-0282"}]}, "Taxonomy_Mappings": {"Taxonomy_Mapping": {"@Taxonomy_Name": "PLOVER", "Entry_Name": "Early Validation Errors"}}, "Related_Attack_Patterns": {"Related_Attack_Pattern": [{"@CAPEC_ID": "3"}, {"@CAPEC_ID": "43"}, {"@CAPEC_ID": "71"}]}, "References": {"Reference": {"@External_Reference_ID": "REF-62", "@Section": "Chapter 8, \"Escaping Metacharacters\", Page 439"}}, "Mapping_Notes": {"Usage": "Allowed", "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.", "Reasons": {"Reason": {"@Type": "Acceptable-Use"}}}, "Notes": {"Note": {"@Type": "Research Gap", "#text": "These errors are mostly reported in path traversal vulnerabilities, but the concept applies whenever validation occurs."}}, "Content_History": {"Submission": {"Submission_Name": "PLOVER", "Submission_Date": "2006-07-19", "Submission_Version": "Draft 3", "Submission_ReleaseDate": "2006-07-19"}, "Modification": [{"Modification_Name": "Eric Dalci", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Potential_Mitigations, Time_of_Introduction"}, {"Modification_Organization": "Veracode", "Modification_Date": "2008-08-15", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "Suggested OWASP Top Ten 2004 mapping"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-09-08", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Modes_of_Introduction, Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-10-14", "Modification_Version": "1.0.1", "Modification_ReleaseDate": "2008-10-14", "Modification_Comment": "updated Description"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-03-10", "Modification_Version": "1.3", "Modification_ReleaseDate": "2009-03-10", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2010-06-21", "Modification_Version": "1.9", "Modification_ReleaseDate": "2010-06-21", "Modification_Comment": "updated Research_Gaps"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-03-29", "Modification_Version": "1.12", "Modification_ReleaseDate": "2011-03-30", "Modification_Comment": "updated Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-06-01", "Modification_Version": "1.13", "Modification_ReleaseDate": "2011-06-01", "Modification_Comment": "updated Common_Consequences"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-05-11", "Modification_Version": "2.2", "Modification_ReleaseDate": "2012-05-15", "Modification_Comment": "updated Common_Consequences, Demonstrative_Examples, Observed_Examples, References, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2014-07-30", "Modification_Version": "2.8", "Modification_ReleaseDate": "2014-07-31", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2017-01-19", "Modification_Version": "2.10", "Modification_ReleaseDate": "2017-01-19", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2017-11-08", "Modification_Version": "3.0", "Modification_ReleaseDate": "2017-11-08", "Modification_Comment": "updated Applicable_Platforms"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-02-24", "Modification_Version": "4.0", "Modification_ReleaseDate": "2020-02-24", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-06-25", "Modification_Version": "4.1", "Modification_ReleaseDate": "2020-06-25", "Modification_Comment": "updated Demonstrative_Examples, Potential_Mitigations, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-01-31", "Modification_Version": "4.10", "Modification_ReleaseDate": "2023-01-31", "Modification_Comment": "updated Description"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-04-27", "Modification_Version": "4.11", "Modification_ReleaseDate": "2023-04-27", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-06-29", "Modification_Version": "4.12", "Modification_ReleaseDate": "2023-06-29", "Modification_Comment": "updated Mapping_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-12-11", "Modification_Version": "4.19", "Modification_ReleaseDate": "2025-12-11", "Modification_Comment": "updated Observed_Examples, Weakness_Ordinalities"}], "Previous_Entry_Name": {"@Date": "2008-04-11", "#text": "Early Validation Errors"}}}