CWE-179: Incorrect Behavior Order: Early ValidationWeakness ID: 179 Vulnerability Mapping:
ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction: BaseBase - 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. |
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. Common Consequences This 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.Scope | Impact | Likelihood |
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Access Control Integrity
| Technical Impact: Bypass Protection Mechanism; Execute Unauthorized Code or Commands 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
Phase: 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 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" (CWE-1000) Nature | Type | ID | Name |
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ChildOf | 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. | 20 | Improper Input Validation | ChildOf | 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. | 696 | Incorrect Behavior Order | ParentOf | 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. | 180 | Incorrect Behavior Order: Validate Before Canonicalize | ParentOf | 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. | 181 | Incorrect Behavior Order: Validate Before Filter |
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. Modes Of Introduction The 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 |
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Implementation | 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. |
Demonstrative Examples Example 1 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/". (bad code) Example Language: Java
String path = getInputPath(); if (path.startsWith("/safe_dir/")) { File f = new File(path); return f.getCanonicalPath(); }
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. (good code) Example Language: Java
String path = getInputPath(); File f = new File(path); if (f.getCanonicalPath().startsWith("/safe_dir/")) { return f.getCanonicalPath(); }
Example 2 This script creates a subdirectory within a user directory and sets the user as the owner. (bad code) Example Language: PHP
function createDir($userName,$dirName){ $userDir = '/users/'. $userName; if(strpos($dirName,'..') !== false){ echo 'Directory name contains invalid sequence'; return; }
//filter out '~' because other scripts identify user directories by this prefix
$dirName = str_replace('~','',$dirName); $newDir = $userDir . $dirName; mkdir($newDir, 0700); chown($newDir,$userName); }
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 Reference | Description |
| Product allows remote attackers to view restricted files via an HTTP request containing a "*" (wildcard or asterisk) character. |
| 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. |
| 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. |
| Overlaps "fakechild/../realchild" |
| Product checks URI for "<" and other literal characters, but does it before hex decoding the URI, so "%3E" and other sequences are allowed. |
| 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. |
| Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a ".." sequence. |
Memberships This 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. Vulnerability Mapping Notes Usage: ALLOWED (this CWE ID could 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 errors are mostly reported in path traversal vulnerabilities, but the concept applies whenever validation occurs. Taxonomy Mappings Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
PLOVER | | | Early Validation Errors |
References
[REF-62] Mark Dowd, John McDonald
and Justin Schuh. "The Art of Software Security Assessment". Chapter 8, "Escaping Metacharacters", Page 439. 1st Edition. Addison Wesley. 2006.
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Content History Submissions |
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Submission Date | Submitter | Organization |
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2006-07-19 (CWE Draft 3, 2006-07-19) | PLOVER | | | Modifications |
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Modification Date | Modifier | Organization |
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2008-07-01 | Eric Dalci | Cigital | updated Potential_Mitigations, Time_of_Introduction | 2008-08-15 | | Veracode | Suggested OWASP Top Ten 2004 mapping | 2008-09-08 | CWE Content Team | MITRE | updated Modes_of_Introduction, Relationships, Taxonomy_Mappings | 2008-10-14 | CWE Content Team | MITRE | updated Description | 2009-03-10 | CWE Content Team | MITRE | updated Relationships | 2010-06-21 | CWE Content Team | MITRE | updated Research_Gaps | 2011-03-29 | CWE Content Team | MITRE | updated Potential_Mitigations | 2011-06-01 | CWE Content Team | MITRE | updated Common_Consequences | 2012-05-11 | CWE Content Team | MITRE | updated Common_Consequences, Demonstrative_Examples, Observed_Examples, References, Relationships | 2014-07-30 | CWE Content Team | MITRE | updated Relationships | 2017-01-19 | CWE Content Team | MITRE | updated Relationships | 2017-11-08 | CWE Content Team | MITRE | updated Applicable_Platforms | 2020-02-24 | CWE Content Team | MITRE | updated Relationships | 2020-06-25 | CWE Content Team | MITRE | updated Demonstrative_Examples, Potential_Mitigations, Relationships | 2023-01-31 | CWE Content Team | MITRE | updated Description | 2023-04-27 | CWE Content Team | MITRE | updated Relationships | 2023-06-29 | CWE Content Team | MITRE | updated Mapping_Notes | Previous Entry Names |
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Change Date | Previous Entry Name |
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2008-04-11 | Early Validation Errors | |
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