88%
27%
98%
An elevation of privilege vulnerability exists when the Windows Background Intelligent Transfer Service (BITS) IIS module improperly handles uploaded content, aka 'Windows Background Intelligent Transfer Service Elevation of Privilege Vulnerability'.
CVSS 3.1 Base Score 8.8. 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:H).
CVSS 2.0 Base Score 6.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:S/C:P/I:P/A:P).
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".
</form>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.
}// Define the target location where the picture being// uploaded is going to be saved.// Move the uploaded file to the new location.echo "The picture has been successfully uploaded.";echo "There was an error uploading the picture, please try again.";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:
malicious.phpSince this filename ends in ".php" it can be executed by the web server. In the contents of this uploaded file, the attacker could use:
?>system($_GET['cmd']);Once this file has been installed, the attacker can enter arbitrary commands to execute using a URL such as:
http://server.example.com/upload_dir/malicious.php?cmd=ls%20-lwhich runs the "ls -l" command - or any other type of command that the attacker wants to specify.
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>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.
}
{...}
// output successful upload response HTML page
bw.close();}bw.flush();...As with the previous example 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.
Additionally, the creation of the BufferedWriter object is subject to relative path traversal (CWE-22, CWE-23). 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.
This code temporarily raises the program's privileges to allow creation of a new user folder.
return True
return False#avoid CWE-22 and CWE-78lowerPrivileges()return FalseWhile the program only raises its privilege level to create the folder and immediately lowers it again, if the call to os.mkdir() throws an exception, the call to lowerPrivileges() will not occur. As a result, the program is indefinitely operating in a raised privilege state, possibly allowing further exploitation to occur.
Evidence of privilege change:
seteuid(getuid());/* do some stuff */
}
// privileged code goes here, for example:// nothing to returnThis code intends to allow only Administrators to print debug information about a system.
}ADMIN,USER,GUEST
}
}
break;break;System.out.println("You must be logged in to perform this command");While the intention was to only allow Administrators to print the debug information, the code as written only excludes those the with the role of "GUEST". Someone with the role of "ADMIN" or "USER" will be allowed access, which goes against the original intent. An attacker may be able to use this debug information to craft an attack on the system.
This code allows someone with the role of "ADMIN" or "OPERATOR" to reset a user's password. The role of "OPERATOR" is intended to have less privileges than an "ADMIN", but still be able to help users with small issues such as forgotten passwords.
}ADMIN,OPERATOR,USER,GUEST
}
}
}break;break;break;System.out.println("You must be logged in to perform this command");This code does not check the role of the user whose password is being reset. It is possible for an Operator to gain Admin privileges by resetting the password of an Admin account and taking control of that account.
ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.
If you'd like to report a bug or have any suggestions for improvements then please do get in touch with us using this form. We will get back to you as soon as we can.