CWE-23: Relative Path TraversalWeakness ID: 23 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 uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory. Extended Description This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory. Alternate Terms
Zip Slip: | "Zip slip" is an attack that uses file archives (e.g., ZIP, tar, rar, etc.) that contain filenames with path traversal sequences that cause the files to be written outside of the directory under which the archive is expected to be extracted [ REF-1282]. It is most commonly used for relative path traversal ( CWE-23) and link following ( CWE-59). |
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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Integrity Confidentiality Availability
| Technical Impact: Execute Unauthorized Code or Commands The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries. | | Integrity
| Technical Impact: Modify Files or Directories The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication. | | Confidentiality
| Technical Impact: Read Files or Directories The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system. | | Availability
| Technical Impact: DoS: Crash, Exit, or Restart The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of a protection mechanisms such as authentication, it has the potential to lockout every user of the product. | |
Potential Mitigations
Phase: 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. |
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. 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). This includes: |
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 | 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') | 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. | 24 | Path Traversal: '../filedir' | 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. | 25 | Path Traversal: '/../filedir' | 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. | 26 | Path Traversal: '/dir/../filename' | 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. | 27 | Path Traversal: 'dir/../../filename' | 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. | 28 | Path Traversal: '..\filedir' | 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. | 29 | Path Traversal: '\..\filename' | 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. | 30 | Path Traversal: '\dir\..\filename' | 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. | 31 | Path Traversal: 'dir\..\..\filename' | 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. | 32 | Path Traversal: '...' (Triple Dot) | 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. | 33 | Path Traversal: '....' (Multiple Dot) | 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. | 34 | Path Traversal: '....//' | 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. | 35 | Path Traversal: '.../...//' |
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 "CISQ Quality Measures (2020)" (CWE-1305) Nature | Type | ID | Name |
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ChildOf | 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') |
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 "CISQ Data Protection Measures" (CWE-1340) Nature | Type | ID | Name |
---|
ChildOf | 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') |
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. Demonstrative Examples Example 1 The following URLs are vulnerable to this attack:
http://example.com.br/get-files.jsp?file=report.pdf http://example.com.br/get-page.php?home=aaa.html http://example.com.br/some-page.asp?page=index.html
A simple way to execute this attack is like this:
http://example.com.br/get-files?file=../../../../somedir/somefile http://example.com.br/../../../../etc/shadow http://example.com.br/get-files?file=../../../../etc/passwd
Example 2 The following code could be for a social networking application in which each user's profile information is stored in a separate file. All files are stored in a single directory. (bad code) Example Language: Perl
my $dataPath = "/users/cwe/profiles"; my $username = param("user"); my $profilePath = $dataPath . "/" . $username;
open(my $fh, "<", $profilePath) || ExitError("profile read error: $profilePath"); print "<ul>\n"; while (<$fh>) { print "<li>$_</li>\n"; } print "</ul>\n";
While the programmer intends to access files such as "/users/cwe/profiles/alice" or "/users/cwe/profiles/bob", there is no verification of the incoming user parameter. An attacker could provide a string such as: The program would generate a profile pathname like this:
/users/cwe/profiles/../../../etc/passwd
When the file is opened, the operating system resolves the "../" during path canonicalization and actually accesses this file: As a result, the attacker could read the entire text of the password file. Notice how this code also contains an error message information leak (CWE-209) if the user parameter does not produce a file that exists: the full pathname is provided. Because of the lack of output encoding of the file that is retrieved, there might also be a cross-site scripting problem (CWE-79) if profile contains any HTML, but other code would need to be examined. Example 3 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. (good code) Example Language: HTML
<form action="FileUploadServlet" method="post" enctype="multipart/form-data">
Choose a file to upload: <input type="file" name="filename"/> <br/> <input type="submit" name="submit" value="Submit"/>
</form>
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. (bad code) Example Language: Java
public class FileUploadServlet extends HttpServlet {
...
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html"); PrintWriter out = response.getWriter(); String contentType = request.getContentType();
// the starting position of the boundary header int ind = contentType.indexOf("boundary="); String boundary = contentType.substring(ind+9);
String pLine = new String(); String uploadLocation = new String(UPLOAD_DIRECTORY_STRING); //Constant value
// verify that content type is multipart form data if (contentType != null && contentType.indexOf("multipart/form-data") != -1) {
// extract the filename from the Http header BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream())); ... pLine = br.readLine(); String filename = pLine.substring(pLine.lastIndexOf("\\"), pLine.lastIndexOf("\"")); ...
// output the file to the local upload directory try {
BufferedWriter bw = new BufferedWriter(new FileWriter(uploadLocation+filename, true)); for (String line; (line=br.readLine())!=null; ) { if (line.indexOf(boundary) == -1) { bw.write(line); bw.newLine(); bw.flush(); } } //end of for loop bw.close();
} catch (IOException ex) {...} // output successful upload response HTML page
} // output unsuccessful upload response HTML page else {...}
} ...
}
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. Observed Examples Reference | Description |
| Large language model (LLM) management tool does not validate the format of a digest value ( CWE-1287) from a private, untrusted model registry, enabling relative path traversal ( CWE-23), a.k.a. Probllama |
| 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) |
| Python package manager does not correctly restrict the filename specified in a Content-Disposition header, allowing arbitrary file read using path traversal sequences such as "../" |
| directory traversal in Go-based Kubernetes operator app allows accessing data from the controller's pod file system via ../ sequences in a yaml file |
| a Kubernetes package manager written in Go allows malicious plugins to inject path traversal sequences into a plugin archive ("Zip slip") to copy a file outside the intended directory |
| Chain: Cloud computing virtualization platform does not require authentication for upload of a tar format file ( CWE-306), then uses .. path traversal sequences ( CWE-23) in the file to access unexpected files, as exploited in the wild per CISA KEV. |
| Go-based archive library allows extraction of files to locations outside of the target folder with "../" path traversal sequences in filenames in a zip file, aka "Zip Slip" |
| Server allows remote attackers to cause a denial of service via certain HTTP GET requests containing a %2e%2e (encoded dot-dot), several "/../" sequences, or several "../" in a URI. |
| "\" not in denylist for web server, allowing path traversal attacks when the server is run in Windows and other OSes. |
| Arbitrary files may be read files via ..\ (dot dot) sequences in an HTTP request. |
| Directory traversal vulnerability in search engine for web server allows remote attackers to read arbitrary files via "..\" sequences in queries. |
| Directory traversal vulnerability in FTP server allows remote attackers to read arbitrary files via "..\" sequences in a GET request. |
| Directory traversal vulnerability in servlet allows remote attackers to execute arbitrary commands via "..\" sequences in an HTTP request. |
| Protection mechanism checks for "/.." but doesn't account for Windows-specific "\.." allowing read of arbitrary files. |
| Directory traversal vulnerability in FTP server allows remote authenticated attackers to list arbitrary directories via a "\.." sequence in an LS command. |
| The administration function in Access Control Server allows remote attackers to read HTML, Java class, and image files outside the web root via a "..\.." sequence in the URL to port 2002. |
| "\..." in web server |
| "..." in cd command in FTP server |
| "..." in cd command in FTP server |
| "..." in cd command in FTP server |
| read of arbitrary files and directories using GET or CD with "..." in Windows-based FTP server. |
| read files using "." and Unicode-encoded "/" or "\" characters in the URL. |
| Directory listing of web server using "..." |
| Triple dot |
| read files via "/........../" in URL |
| read files via "...." in web server |
| read files via "......" in web server (doubled triple dot?) |
| read files via "......" in web server (doubled triple dot?) |
| multiple attacks using "..", "...", and "...." in different commands |
| "..." or "...." in chat server |
| chain: ".../...//" bypasses protection mechanism using regexp's that remove "../" resulting in collapse into an unsafe value "../" ( CWE-182) and resultant path traversal. |
| ".../....///" bypasses regexp's that remove "./" and "../" |
| Mail server allows remote attackers to create arbitrary directories via a ".." or rename arbitrary files via a "....//" in user supplied parameters. |
Detection Methods
Automated Static Analysis Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.) |
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. |
Taxonomy Mappings Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
PLOVER | | | Relative Path Traversal |
Software Fault Patterns | SFP16 | | Path Traversal |
References
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[REF-62] Mark Dowd, John McDonald
and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Filenames and Paths", Page 503. 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 | | | Contributions |
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Contribution Date | Contributor | Organization |
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2022-07-11 | Nick Johnston | | Identified weakness in Perl demonstrative example | Modifications |
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Modification Date | Modifier | Organization |
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2008-07-01 | Eric Dalci | Cigital | updated References, Demonstrative_Example, Potential_Mitigations, Time_of_Introduction | 2008-09-08 | CWE Content Team | MITRE | updated Relationships, References, Taxonomy_Mappings | 2008-10-14 | CWE Content Team | MITRE | updated Description | 2009-07-27 | CWE Content Team | MITRE | updated Potential_Mitigations | 2010-02-16 | CWE Content Team | MITRE | updated Demonstrative_Examples | 2010-06-21 | CWE Content Team | MITRE | updated Description, Potential_Mitigations | 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, Taxonomy_Mappings | 2017-01-19 | CWE Content Team | MITRE | updated Related_Attack_Patterns | 2017-11-08 | CWE Content Team | MITRE | updated Applicable_Platforms | 2019-06-20 | CWE Content Team | MITRE | updated Related_Attack_Patterns | 2020-02-24 | CWE Content Team | MITRE | updated Potential_Mitigations, Relationships | 2020-06-25 | CWE Content Team | MITRE | updated Observed_Examples, Potential_Mitigations | 2020-08-20 | CWE Content Team | MITRE | updated Relationships | 2020-12-10 | CWE Content Team | MITRE | updated Relationships | 2021-03-15 | CWE Content Team | MITRE | updated Demonstrative_Examples | 2021-10-28 | CWE Content Team | MITRE | updated Relationships | 2022-06-28 | CWE Content Team | MITRE | updated Observed_Examples | 2022-10-13 | CWE Content Team | MITRE | updated Alternate_Terms, Observed_Examples, References | 2023-01-31 | CWE Content Team | MITRE | updated Common_Consequences, Description | 2023-04-27 | CWE Content Team | MITRE | updated Detection_Factors, Relationships | 2023-06-29 | CWE Content Team | MITRE | updated Mapping_Notes | 2023-10-26 | CWE Content Team | MITRE | updated Observed_Examples | 2024-07-16 (CWE 4.15, 2024-07-16) | CWE Content Team | MITRE | updated Observed_Examples, References |
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