CWE-179: Incorrect Behavior Order: Early Validation

Q: What is CWE-179: Incorrect Behavior Order: Early Validation?

CWE-179: Incorrect Behavior Order: Early Validation is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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. 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.

Q: What are the security consequences of Incorrect Behavior Order: Early Validation?

If exploited, CWE-179 (Incorrect Behavior Order: Early Validation) it can compromise Access Control and Integrity, leading to outcomes such as Bypass Protection Mechanism and Execute Unauthorized Code or Commands.

Q: Which programming languages are affected by Incorrect Behavior Order: Early Validation?

CWE-179 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

Q: What are real-world examples of Incorrect Behavior Order: Early Validation?

MITRE documents real CVEs mapped to CWE-179, including CVE-2002-0433, CVE-2003-0332, CVE-2002-0802, CVE-2000-0191 and CVE-2004-2363. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

Q: What is the difference between a CWE and a CVE?

A CWE (Common Weakness Enumeration) like CWE-179 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.

Code Examples & CVEs

Demonstrative Examples

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/".

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 "/".

BadJava

String path = getInputPath();if (path.startsWith("/safe_dir/")){File f = new File(path);return f.getCanonicalPath();}

GoodJava

String path = getInputPath();File f = new File(path);if (f.getCanonicalPath().startsWith("/safe_dir/")){return f.getCanonicalPath();}

This script creates a subdirectory within a user directory and sets the user as the owner.

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.

BadPHP

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);}

Observed CVE Examples (7)

CVE-2002-0433

List files in web server using "*.ext"

View Details

CVE-2003-0332

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.

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CVE-2002-0802

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.

View Details

CVE-2000-0191

Overlaps "fakechild/../realchild"

View Details

CVE-2004-2363

Product checks URI for "<" and other literal characters, but does it before hex decoding the URI, so "%3E" and other sequences are allowed.

View Details

CVE-2002-0934

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.

View Details

CVE-2003-0282

Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a ".." sequence.

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-179 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-179, Incorrect Behavior Order: Early Validation, 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 Incorrect Behavior Order: Early Validation

MITRE associates mitigation with Implementation; the listed strategies include Input Validation; recorded impacts include Bypass Protection Mechanism, and Execute Unauthorized Code or Commands. Use these source-defined anchors to turn CWE-179 into implementation, review, and verification checks for the affected component.

CWE-179: Incorrect Behavior Order: Early Validation — MITRE CWE

Triage CWE-179 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-179, Incorrect Behavior Order: Early Validation, 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-179

Apply MITRE's full root-cause mapping guidance when using CWE-179, Incorrect Behavior Order: Early Validation. 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-179 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-179, Incorrect Behavior Order: Early Validation. 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-179: Incorrect Behavior Order: Early Validation?+

CWE-179: Incorrect Behavior Order: Early Validation is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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. 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.

What are the security consequences of Incorrect Behavior Order: Early Validation?+

If exploited, CWE-179 (Incorrect Behavior Order: Early Validation) it can compromise Access Control and Integrity, leading to outcomes such as Bypass Protection Mechanism and Execute Unauthorized Code or Commands.

Which programming languages are affected by Incorrect Behavior Order: Early Validation?+

CWE-179 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 Incorrect Behavior Order: Early Validation?+

MITRE documents real CVEs mapped to CWE-179, including CVE-2002-0433, CVE-2003-0332, CVE-2002-0802, CVE-2000-0191 and CVE-2004-2363. 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-179 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-179: Incorrect Behavior Order: Early Validation

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (7)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-179 with SSDF evidence

Apply Input Validation controls for Incorrect Behavior Order: Early Validation

Triage CWE-179 against known exploitation evidence

Apply precise root-cause mapping to CWE-179

Validate CWE-179 with root-cause mapping checks

Frequently Asked Questions

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