| Impact | Details |
|---|---|
|
Execute Unauthorized Code or Commands |
Scope: Integrity, Confidentiality, Availability
Arbitrary code execution is possible if an uploaded file is interpreted and executed as code by the recipient. This is especially true for web-server extensions such as .asp and .php because these file types are often treated as automatically executable, even when file system permissions do not specify execution. For example, in Unix environments, programs typically cannot run unless the execute bit is set, but PHP programs may be executed by the web server without directly invoking them on the operating system.
|
| Phase(s) | Mitigation |
|---|---|
|
Architecture and Design |
|
|
Architecture and Design |
Strategy: Enforcement by Conversion When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
|
|
Architecture and Design |
Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically. [REF-423]
|
|
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. For example, limiting filenames to alphanumeric characters can help to restrict the introduction of unintended file extensions. |
|
Architecture and Design |
Define a very limited set of allowable extensions and only generate filenames that end in these extensions. Consider the possibility of XSS (CWE-79) before allowing .html or .htm file types.
|
|
Implementation |
Strategy: Input Validation |
|
Implementation |
When running on a web server that supports case-insensitive filenames, perform case-insensitive evaluations of the extensions that are provided.
|
|
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 |
Do not rely exclusively on sanity checks of file contents to ensure that the file is of the expected type and size. It may be possible for an attacker to hide code in some file segments that will still be executed by the server. For example, GIF images may contain a free-form comments field.
|
|
Implementation |
Do not rely exclusively on the MIME content type or filename attribute when determining how to render a file. Validating the MIME content type and ensuring that it matches the extension is only a partial solution.
|
|
Architecture and Design; Operation |
Strategy: Environment Hardening Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
|
|
Architecture and Design; Operation |
Strategy: Sandbox or Jail Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails. Effectiveness: Limited Note:
The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.
|
| 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. | 669 | Incorrect Resource Transfer Between Spheres |
| PeerOf | 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. | 351 | Insufficient Type Distinction |
| PeerOf | 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. | 430 | Deployment of Wrong Handler |
| PeerOf | 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. | 436 | Interpretation Conflict |
| CanFollow | 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. | 73 | External Control of File Name or Path |
| CanFollow | 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. | 183 | Permissive List of Allowed Inputs |
| CanFollow | 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. | 184 | Incomplete List of Disallowed Inputs |
| Nature | Type | ID | Name |
|---|---|---|---|
| MemberOf | Category Category - a CWE entry that contains a set of other entries that share a common characteristic. | 429 | Handler Errors |
| 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. | 669 | Incorrect Resource Transfer Between Spheres |
| Nature | Type | ID | Name |
|---|---|---|---|
| MemberOf | Category Category - a CWE entry that contains a set of other entries that share a common characteristic. | 1011 | Authorize Actors |
| Phase | Note |
|---|---|
| Implementation | |
| Architecture and Design | OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase. |
ASP.NET (Sometimes Prevalent)
PHP (Often Prevalent)
Class: Not Language-Specific (Undetermined Prevalence)
Web Server (Sometimes Prevalent)
Example 1
The following code intends to allow a user to upload a picture to the web server. The HTML code that drives the form on the user end has an input field of type "file".
Once submitted, the form above sends the file to upload_picture.php on the web server. PHP stores the file in a temporary location until it is retrieved (or discarded) by the server side code. In this example, the file is moved to a more permanent pictures/ directory.
The problem with the above code is that there is no check regarding type of file being uploaded. Assuming that pictures/ is available in the web document root, an attacker could upload a file with the name:
Since this filename ends in ".php" it can be executed by the web server. In the contents of this uploaded file, the attacker could use:
Once this file has been installed, the attacker can enter arbitrary commands to execute using a URL such as:
which runs the "ls -l" command - or any other type of command that the attacker wants to specify.
Example 2
The following code demonstrates the unrestricted upload of a file with a Java servlet and a path traversal vulnerability. The action attribute of an HTML form is sending the upload file request to the Java servlet.
When submitted the Java servlet's doPost method will receive the request, extract the name of the file from the Http request header, read the file contents from the request and output the file to the local upload directory.
This code does not perform a check on the type of the file being uploaded (CWE-434). This could allow an attacker to upload any executable file or other file with malicious code.
Additionally, the creation of the BufferedWriter object is subject to relative path traversal (CWE-23). Since the code does not check the filename that is provided in the header, an attacker can use "../" sequences to write to files outside of the intended directory. Depending on the executing environment, the attacker may be able to specify arbitrary files to write to, leading to a wide variety of consequences, from code execution, XSS (CWE-79), or system crash.
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 |
|---|---|
|
PHP-based FAQ management app does not check the MIME type for uploaded images
|
|
|
Web-based mail product stores ".shtml" attachments that could contain SSI
|
|
|
PHP upload does not restrict file types
|
|
|
upload and execution of .php file
|
|
|
upload file with dangerous extension
|
|
|
program does not restrict file types
|
|
|
improper type checking of uploaded files
|
|
|
Double "php" extension leaves an active php extension in the generated filename.
|
|
|
ASP program allows upload of .asp files by bypassing client-side checks
|
|
|
ASP file upload
|
|
|
ASP file upload
|
| Ordinality | Description |
|---|---|
|
Primary
|
(where the weakness exists independent of other weaknesses)
This can be primary when there is no check for the file type at all.
|
Resultant
|
(where the weakness is typically related to the presence of some other weaknesses)
This can be resultant when use of double extensions (e.g. ".php.gif") bypasses a check.
|
Resultant
|
(where the weakness is typically related to the presence of some other weaknesses)
This can be resultant from client-side enforcement (CWE-602); some products will include web script in web clients to check the filename, without verifying on the server side.
|
| Method | Details |
|---|---|
|
Dynamic Analysis with Automated Results Interpretation |
According to SOAR [REF-1479], the following detection techniques may be useful: Cost effective for partial coverage:
Effectiveness: SOAR Partial |
|
Dynamic Analysis with Manual Results Interpretation |
According to SOAR [REF-1479], the following detection techniques may be useful: Cost effective for partial coverage:
Effectiveness: SOAR Partial |
|
Manual Static Analysis - Source Code |
According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective:
Effectiveness: High |
|
Automated Static Analysis - Source Code |
According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective:
Effectiveness: High |
|
Architecture or Design Review |
According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective:
Cost effective for partial coverage:
Effectiveness: High |
| Nature | Type | ID | Name |
|---|---|---|---|
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 714 | OWASP Top Ten 2007 Category A3 - Malicious File Execution |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 801 | 2010 Top 25 - Insecure Interaction Between Components |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 813 | OWASP Top Ten 2010 Category A4 - Insecure Direct Object References |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 864 | 2011 Top 25 - Insecure Interaction Between Components |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 884 | CWE Cross-section |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 1131 | CISQ Quality Measures (2016) - Security |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1200 | Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 1308 | CISQ Quality Measures - Security |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1337 | Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1340 | CISQ Data Protection Measures |
| 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 | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1350 | Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 1364 | ICS Communications: Zone Boundary Failures |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1387 | Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses |
| MemberOf | CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. | 1416 | Comprehensive Categorization: Resource Lifecycle Management |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1425 | Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses |
| MemberOf | ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). | 1430 | Weaknesses in the 2024 CWE Top 25 Most Dangerous Software Weaknesses |
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.Relationship
This can have a chaining relationship with incomplete denylist / permissive allowlist errors when the product tries, but fails, to properly limit which types of files are allowed (CWE-183, CWE-184).
This can also overlap multiple interpretation errors for intermediaries, e.g. anti-virus products that do not remove or quarantine attachments with certain file extensions that can be processed by client systems.
| Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
|---|---|---|---|
| PLOVER | Unrestricted File Upload | ||
| OWASP Top Ten 2007 | A3 | CWE More Specific | Malicious File Execution |
| OMG ASCSM | ASCSM-CWE-434 |
| CAPEC-ID | Attack Pattern Name |
|---|---|
| CAPEC-1 | Accessing Functionality Not Properly Constrained by ACLs |
| Submissions | |||
|---|---|---|---|
| Submission Date | Submitter | Organization | |
|
2006年07月19日
(CWE Draft 3, 2006年07月19日) |
PLOVER | ||
| Contributions | |||
| Contribution Date | Contributor | Organization | |
|
2024年02月29日
(CWE 4.15, 2024年07月16日) |
Abhi Balakrishnan | ||
| Provided diagram to improve CWE usability | |||
| Modifications | |||
| Modification Date | Modifier | Organization | |
|
2025年09月09日
(CWE 4.18, 2025年09月09日) |
CWE Content Team | MITRE | |
| updated Detection_Factors, References | |||
|
2024年11月19日
(CWE 4.16, 2024年11月19日) |
CWE Content Team | MITRE | |
| updated Relationships | |||
|
2024年07月16日
(CWE 4.15, 2024年07月16日) |
CWE Content Team | MITRE | |
| updated Common_Consequences, Description, Diagram, Weakness_Ordinalities | |||
|
2024年02月29日
(CWE 4.14, 2024年02月29日) |
CWE Content Team | MITRE | |
| updated Observed_Examples | |||
| 2023年06月29日 | CWE Content Team | MITRE | |
| updated Mapping_Notes, Relationships | |||
| 2023年04月27日 | CWE Content Team | MITRE | |
| updated References, Relationships | |||
| 2023年01月31日 | CWE Content Team | MITRE | |
| updated Alternate_Terms, Description | |||
| 2022年10月13日 | CWE Content Team | MITRE | |
| updated References | |||
| 2022年06月28日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2022年04月28日 | CWE Content Team | MITRE | |
| updated Research_Gaps | |||
| 2021年10月28日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2021年07月20日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2021年03月15日 | CWE Content Team | MITRE | |
| updated Demonstrative_Examples | |||
| 2020年12月10日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2020年08月20日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2020年06月25日 | CWE Content Team | MITRE | |
| updated Potential_Mitigations, Relationship_Notes | |||
| 2020年02月24日 | CWE Content Team | MITRE | |
| updated Applicable_Platforms, Potential_Mitigations | |||
| 2019年09月19日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2019年06月20日 | CWE Content Team | MITRE | |
| updated Related_Attack_Patterns | |||
| 2019年01月03日 | CWE Content Team | MITRE | |
| updated References, Relationships, Taxonomy_Mappings | |||
| 2017年11月08日 | CWE Content Team | MITRE | |
| updated Affected_Resources, Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships, Weakness_Ordinalities | |||
| 2015年12月07日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2014年07月30日 | CWE Content Team | MITRE | |
| updated Detection_Factors | |||
| 2012年10月30日 | CWE Content Team | MITRE | |
| updated Potential_Mitigations | |||
| 2012年05月11日 | CWE Content Team | MITRE | |
| updated References, Relationships | |||
| 2011年09月13日 | CWE Content Team | MITRE | |
| updated Potential_Mitigations, References, Relationships | |||
| 2011年06月27日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2010年12月13日 | CWE Content Team | MITRE | |
| updated Potential_Mitigations | |||
| 2010年09月27日 | CWE Content Team | MITRE | |
| updated Potential_Mitigations | |||
| 2010年06月21日 | CWE Content Team | MITRE | |
| updated References, Relationship_Notes | |||
| 2010年04月05日 | CWE Content Team | MITRE | |
| updated Related_Attack_Patterns | |||
| 2010年02月16日 | CWE Content Team | MITRE | |
| updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Name, Other_Notes, Potential_Mitigations, References, Related_Attack_Patterns, Relationship_Notes, Relationships, Type, Weakness_Ordinalities | |||
| 2010年02月16日 | CWE Content Team | MITRE | |
| converted from Compound_Element to Weakness | |||
| 2009年12月28日 | CWE Content Team | MITRE | |
| updated Applicable_Platforms, Functional_Areas, Likelihood_of_Exploit, Potential_Mitigations, Time_of_Introduction | |||
| 2009年01月12日 | CWE Content Team | MITRE | |
| updated Relationships | |||
| 2008年09月08日 | CWE Content Team | MITRE | |
| updated Alternate_Terms, Relationships, Other_Notes, Taxonomy_Mappings | |||
| 2008年07月01日 | Eric Dalci | Cigital | |
| updated Time_of_Introduction | |||
| Previous Entry Names | |||
| Change Date | Previous Entry Name | ||
| 2010年02月16日 | Unrestricted File Upload | ||
Use of the Common Weakness Enumeration (CWE™) and the associated references from this website are subject to the Terms of Use. CWE is sponsored by the U.S. Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA) and managed by the Homeland Security Systems Engineering and Development Institute (HSSEDI) which is operated by The MITRE Corporation (MITRE). Copyright © 2006–2025, The MITRE Corporation. CWE, CWSS, CWRAF, and the CWE logo are trademarks of The MITRE Corporation.