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TheoMitre CWE

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Dữ liệu MITRE CWE chính thức

Tên gọi khác

Unrestricted File Upload — Used in vulnerability databases and elsewhere, but it is insufficiently precise. The phrase could be interpreted as the lack of restrictions on the size or number of uploaded files, which is a resource consumption issue.

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Hiện thực hóa
Kiến trúc và thiết kế: OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.

Hậu quả thường gặp

Dữ liệu MITRE CWE chính thức

Tác động	Phạm vi	Diễn giải
Thực thi mã hoặc lệnh trái phép	Tính toàn vẹn, Tính bí mật, Tính sẵn sàng	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.

Biện pháp giảm thiểu rủi ro

Dữ liệu MITRE CWE chính thức

Kiến trúc và thiết kếGenerate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.[REF-422] [REF-423]
Áp đặt quy tắc bằng chuyển đổi · Kiến trúc và thiết kếWhen 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.
Kiến trúc và thiết kếConsider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically. [REF-423]
Kiểm tra dữ liệu đầu vào · Hiện thực hóaAssume 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.
Kiến trúc và thiết kếDefine 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.
Kiểm tra dữ liệu đầu vào · Hiện thực hóaEnsure that only one extension is used in the filename. Some web servers, including some versions of Apache, may process files based on inner extensions so that "filename.php.gif" is fed to the PHP interpreter.[REF-422] [REF-423]
Hiện thực hóaWhen running on a web server that supports case-insensitive filenames, perform case-insensitive evaluations of the extensions that are provided.
Kiến trúc và thiết kếFor 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.
Hiện thực hóaDo 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.
Hiện thực hóaDo 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.
Gia cố môi trường · Kiến trúc và thiết kế, Vận hànhRun 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.
Môi trường cô lập (sandbox/jail) · Kiến trúc và thiết kế, Vận hành · Hiệu quả: Hạn chếRun 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.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.

Cách phát hiện trong hệ thống

Dữ liệu MITRE CWE chính thức

Phương pháp	Cách làm	Hiệu quả
Phân tích động với diễn giải kết quả tự động	According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Web Application Scanner Web Services Scanner Database Scanners	SOAR một phần
Phân tích động với diễn giải kết quả thủ công	According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Fuzz Tester Framework-based Fuzzer	SOAR một phần
Phân tích tĩnh mã nguồn thủ công	According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)	Cao
Phân tích tĩnh mã nguồn tự động	According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer	Cao
Rà soát kiến trúc hoặc thiết kế	According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Formal Methods / Correct-By-Construction ``` Cost effective for partial coverage: ``` Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)	Cao

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Dữ liệu MITRE CWE chính thức

Dưới đây là các lỗ hổng tiêu biểu liên quan đến CWE-434, dựa theo mức độ ưu tiên

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MITRE CWE

CWE Terms of Use

CWE-434: Unrestricted Upload of File with Dangerous Type

CWE-434 là gì?

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