CWE - CWE-73: External Control of File Name or Path (4.20)
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    CWE-73: External Control of File Name or Path

    Weakness ID: 73
    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 allows user input to control or influence paths or file names that are used in filesystem operations.
    + Extended Description

    This could allow an attacker to access or modify system files or other files that are critical to the application.

    Path manipulation errors occur when the following two conditions are met:

    1. An attacker can specify a path used in an operation on the filesystem.
    2. By specifying the resource, the attacker gains a capability that would not otherwise be permitted.

    For example, the program may give the attacker the ability to overwrite the specified file or run with a configuration controlled by the attacker.

    + 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

    Read Files or Directories; Modify Files or Directories

    		Scope: Integrity, Confidentiality

    The application can operate on unexpected files. Confidentiality is violated when the targeted filename is not directly readable by the attacker.

    Modify Files or Directories; Execute Unauthorized Code or Commands

    		Scope: Integrity, Confidentiality, Availability

    The application can operate on unexpected files. This may violate integrity if the filename is written to, or if the filename is for a program or other form of executable code.

    DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Other)

    		Scope: Availability

    The application can operate on unexpected files. Availability can be violated if the attacker specifies an unexpected file that the application modifies. Availability can also be affected if the attacker specifies a filename for a large file, or points to a special device or a file that does not have the format that the application expects.
    + Potential Mitigations
    Phase(s) Mitigation

    Architecture and Design
    When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap provide this capability.

    Architecture and Design; Operation

    Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.

    Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection.

    This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise.

    Be careful to avoid CWE-243 and other weaknesses related to jails.

    Architecture and Design
    For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

    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.

    When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.

    Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

    Effectiveness: High

    Implementation
    Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59).

    Installation; Operation
    Use OS-level permissions and run as a low-privileged user to limit the scope of any successful attack.

    Operation; Implementation
    If you are using PHP, configure your application so that it does not use register_globals. During implementation, develop your application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

    Testing
    Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
    + 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. 610 Externally Controlled Reference to a Resource in Another Sphere
    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. 642 External Control of Critical State Data
    ParentOf 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. 114 Process Control
    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. 22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
    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. 41 Improper Resolution of Path Equivalence
    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. 59 Improper Link Resolution Before File Access ('Link Following')
    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. 98 Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')
    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. 434 Unrestricted Upload of File with Dangerous Type
    + 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. 399 Resource Management Errors
    + Relevant to the view "Architectural Concepts" (View-1008)
    Nature Type ID Name
    MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1015 Limit Access
    + Relevant to the view "Seven Pernicious Kingdoms" (View-700)
    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. 20 Improper Input Validation
    + 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
    Architecture and Design
    Implementation REALIZATION: This weakness is caused during implementation of an architectural security tactic.
    + 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)

    Operating Systems

    Class: Unix (Often Prevalent)

    Class: Windows (Often Prevalent)

    Class: macOS (Often Prevalent)

    + Likelihood Of Exploit
    High
    + Demonstrative Examples

    Example 1


    The following code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files (CWE-22).

    (bad code)
    Example Language: Java 
    String rName = request.getParameter("reportName");
    File rFile = new File("/usr/local/apfr/reports/" + rName);
    ...
    rFile.delete();


    Example 2


    The following code uses input from a configuration file to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can change the configuration file, they can use the program to read any file on the system that ends with the extension .txt.

    (bad code)
    Example Language: Java 
    fis = new FileInputStream(cfg.getProperty("sub")+".txt");
    amt = fis.read(arr);
    out.println(arr);


    + 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
    Chain: a learning management tool debugger uses external input to locate previous session logs (CWE-73) and does not properly validate the given path (CWE-20), allowing for filesystem path traversal using "../" sequences (CWE-24)
    Chain: external control of values for user's desired language and theme enables path traversal.
    Chain: external control of user's target language enables remote file inclusion.
    + Weakness Ordinalities
    Ordinality Description
    Primary
    (where the weakness exists independent of other weaknesses)
    + Detection Methods
    Method Details

    Automated Static Analysis

    The external control or influence of filenames can often be detected using automated static analysis that models data flow within the product.

    Automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or require any code changes.
    + 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. 723 OWASP Top Ten 2004 Category A2 - Broken Access Control
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 752 2009 Top 25 - Risky Resource Management
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 877 CERT C++ Secure Coding Section 09 - Input Output (FIO)
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 981 SFP Secondary Cluster: Path Traversal
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1348 OWASP Top Ten 2021 Category A04:2021 - Insecure Design
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1403 Comprehensive Categorization: Exposed Resource
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1441 OWASP Top Ten 2025 Category A06:2025 - Insecure Design
    + 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

    Relationship

    The external control of filenames can be the primary link in chains with other file-related weaknesses, as seen in the CanPrecede relationships. This is because software systems use files for many different purposes: to execute programs, load code libraries, to store application data, to store configuration settings, record temporary data, act as signals or semaphores to other processes, etc.

    However, those weaknesses do not always require external control. For example, link-following weaknesses (CWE-59) often involve pathnames that are not controllable by the attacker at all.

    The external control can be resultant from other issues. For example, in PHP applications, the register_globals setting can allow an attacker to modify variables that the programmer thought were immutable, enabling file inclusion (CWE-98) and path traversal (CWE-22). Operating with excessive privileges (CWE-250) might allow an attacker to specify an input filename that is not directly readable by the attacker, but is accessible to the privileged program. A buffer overflow (CWE-119) might give an attacker control over nearby memory locations that are related to pathnames, but were not directly modifiable by the attacker.

    Maintenance

    CWE-114 is a Class, but it is listed a child of CWE-73 in view 1000. This suggests some abstraction problems that should be resolved in future versions.
    + Taxonomy Mappings
    Mapped Taxonomy Name Node ID Fit Mapped Node Name
    7 Pernicious Kingdoms Path Manipulation
    Software Fault Patterns SFP16 Path Traversal
    + References
    [REF-6] Katrina Tsipenyuk, Brian Chess and Gary McGraw. "Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors". NIST Workshop on Software Security Assurance Tools Techniques and Metrics. NIST. 2005-11-07.
    <https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf>.
    [REF-45] OWASP. "OWASP Enterprise Security API (ESAPI) Project".
    <https://owasp.org/www-project-enterprise-security-api/>. (URL validated: 2025-07-24)
    + Content History
    + Submissions
    Submission Date Submitter Organization
    2006-07-19
    (CWE Draft 3, 2006-07-19)     		7 Pernicious Kingdoms
    + Modifications
    Modification Date Modifier Organization
    2025-12-11
    (CWE 4.19, 2025-12-11)     		CWE Content Team MITRE
    updated Relationships
    2025-09-09
    (CWE 4.18, 2025-09-09)     		CWE Content Team MITRE
    updated References
    2023-10-26
    (CWE 4.13, 2023-10-26)     		CWE Content Team MITRE
    updated Observed_Examples
    2023-06-29
    (CWE 4.12, 2023-06-29)     		CWE Content Team MITRE
    updated Mapping_Notes
    2023-04-27
    (CWE 4.11, 2023-04-27)     		CWE Content Team MITRE
    updated Potential_Mitigations, Relationships
    2023-01-31
    (CWE 4.10, 2023-01-31)     		CWE Content Team MITRE
    updated Description, Detection_Factors, Potential_Mitigations
    2021-10-28
    (CWE 4.6, 2021-10-28)     		CWE Content Team MITRE
    updated Relationships
    2021-03-15
    (CWE 4.4, 2021-03-15)     		CWE Content Team MITRE
    updated Maintenance_Notes, Potential_Mitigations
    2020-06-25
    (CWE 4.1, 2020-06-25)     		CWE Content Team MITRE
    updated Potential_Mitigations, Relationships
    2020-02-24
    (CWE 4.0, 2020-02-24)     		CWE Content Team MITRE
    updated Potential_Mitigations, References, Relationships, Time_of_Introduction, Type
    2017-11-08
    (CWE 3.0, 2017-11-08)     		CWE Content Team MITRE
    updated Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, Relationships, Taxonomy_Mappings
    2014-07-30
    (CWE 2.8, 2014-07-31)     		CWE Content Team MITRE
    updated Relationships, Taxonomy_Mappings
    2012-10-30
    (CWE 2.3, 2012-10-30)     		CWE Content Team MITRE
    updated Potential_Mitigations
    2012-05-11
    (CWE 2.2, 2012-05-15)     		CWE Content Team MITRE
    updated Demonstrative_Examples, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings
    2011-09-13
    (CWE 2.1, 2011-09-13)     		CWE Content Team MITRE
    updated Relationships, Taxonomy_Mappings
    2011-06-01
    (CWE 1.13, 2011-06-01)     		CWE Content Team MITRE
    updated Common_Consequences, Relationships, Taxonomy_Mappings
    2010-02-16
    (CWE 1.8, 2010-02-16)     		CWE Content Team MITRE
    updated Potential_Mitigations
    2009-12-28
    (CWE 1.7, 2009-12-28)     		CWE Content Team MITRE
    updated Detection_Factors
    2009-10-29
    (CWE 1.6, 2009-10-29)     		CWE Content Team MITRE
    updated Common_Consequences, Description
    2009-07-27
    (CWE 1.5, 2009-07-27)     		CWE Content Team MITRE
    updated Demonstrative_Examples
    2009-03-10
    (CWE 1.3, 2009-03-10)     		CWE Content Team MITRE
    updated Potential_Mitigations, Relationships
    2009-01-12
    (CWE 1.2, 2009-01-12)     		CWE Content Team MITRE
    updated Applicable_Platforms, Causal_Nature, Common_Consequences, Demonstrative_Examples, Description, Observed_Examples, Other_Notes, Potential_Mitigations, References, Relationship_Notes, Relationships, Weakness_Ordinalities
    2008-09-08
    (CWE 1.0, 2008-09-09)     		CWE Content Team MITRE
    updated Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
    2008-07-01
    (CWE 1.0, 2008-09-09)     		Eric Dalci Cigital
    updated Time_of_Introduction
    + Previous Entry Names
    Change Date Previous Entry Name
    2008-04-11 Path Manipulation
    Page Last Updated: April 30, 2026