CVE-2019-3943 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Severity

81%

Complexity

27%

Confidentiality

86%

MikroTik RouterOS versions Stable 6.43.12 and below, Long-term 6.42.12 and below, and Testing 6.44beta75 and below are vulnerable to an authenticated, remote directory traversal via the HTTP or Winbox interfaces. An authenticated, remote attack can use this vulnerability to read and write files outside of the sandbox directory (/rw/disk).

MikroTik RouterOS versions Stable 6.43.12 and below, Long-term 6.42.12 and below, and Testing 6.44beta75 and below are vulnerable to an authenticated, remote directory traversal via the HTTP or Winbox interfaces. An authenticated, remote attack can use this vulnerability to read and write files outside of the sandbox directory (/rw/disk).

CVSS 3.1 Base Score 8.1. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

CVSS 2.0 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:S/C:C/I:P/A:N).

Demo Examples

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-22

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.


               
print "</ul>\n";
print "<li>$_</li>\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:


               
../../../etc/passwd

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:


               
/etc/passwd

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.

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-22

In the example below, the path to a dictionary file is read from a system property and used to initialize a File object.


               
File dictionaryFile = new File(filename);

However, the path is not validated or modified to prevent it from containing relative or absolute path sequences before creating the File object. This allows anyone who can control the system property to determine what file is used. Ideally, the path should be resolved relative to some kind of application or user home directory.

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-22

The following code takes untrusted input and uses a regular expression to filter "../" from the input. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.


               
ReadAndSendFile($filename);

Since the regular expression does not have the /g global match modifier, it only removes the first instance of "../" it comes across. So an input value such as:


               
../../../etc/passwd

will have the first "../" stripped, resulting in:


               
../../etc/passwd

This value is then concatenated with the /home/user/ directory:


               
/home/user/../../etc/passwd

which causes the /etc/passwd file to be retrieved once the operating system has resolved the ../ sequences in the pathname. This leads to relative path traversal (CWE-23).

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-22

The following code attempts to validate a given input path by checking it against a whitelist and once validated delete the given file. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".


               
}
f.delete()

An attacker could provide an input such as this:


               
/safe_dir/../important.dat

The software assumes that the path is valid because it starts with the "/safe_path/" sequence, but the "../" sequence will cause the program to delete the important.dat file in the parent directory

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-22

The following code demonstrates the unrestricted upload of a file with a Java servlet and a path traversal vulnerability. The HTML code is the same as in the previous example with the action attribute of the form sending the upload file request to the Java servlet instead of the PHP code.


               
</form>
<input type="submit" name="submit" value="Submit"/>

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.


               
}
{...}// the starting position of the boundary header// verify that content type is multipart form data
// output the file to the local upload directory
bw.close();
}
bw.flush();
// output successful upload response HTML page
// output unsuccessful upload response HTML page
...

This code does not check the filename that is provided in the header, so 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.

Also, this code does not perform a check on the type of the file being uploaded. This could allow an attacker to upload any executable file or other file with malicious code (CWE-434).

Overview

Type

Mikrotik Routeros

First reported 6 years ago

2019-04-10 21:29:00

Last updated 5 years ago

2019-12-17 19:19:00

Affected Software

Mikrotik Routeros 6.41 Release Candidate 31 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 32 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 34 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 37 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 38 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 44 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 47 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 50 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 52 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 56 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 61 Testing Edition

6.41

Mikrotik Routeros 6.41 Release Candidate 66 Testing Edition

6.41

Mikrotik Routeros 6.42 Release Candidate 11 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 12 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 14 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 15 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 18 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 2 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 20 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 23 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 24 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 27 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 28 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 30 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 35 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 37 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 39 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 41 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 43 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 46 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 48 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 49 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 5 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 52 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 56 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 6 Testing Edition

6.42

Mikrotik Routeros 6.42 Release Candidate 9 Testing Edition

6.42

Mikrotik Routeros 6.43 Release Candidate 11 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 12 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 14 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 17 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 19 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 21 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 23 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 27 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 29 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 3 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 32 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 34 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 4 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 40 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 42 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 44 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 45 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 5 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 51 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 56 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 6 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 64 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 66 Testing Edition

6.43

Mikrotik Routeros 6.43 Release Candidate 7 Testing Edition

6.43

Mikrotik Routeros 6.44 Beta14 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta17 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta20 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta28 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta39 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta40 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta50 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta54 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta6 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta61 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta75 Testing Edition

6.44

Mikrotik Routeros 6.44 Beta9 Testing Edition

6.44

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