[CORE-2014-0010] - Advantech WebAccess Stack-based Buffer Overflow

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

Advantech WebAccess Stack-based Buffer Overflow

1. Advisory Information

Title: Advantech WebAccess Stack-based Buffer Overflow
Advisory ID: CORE-2014-0010
Advisory URL:
http://www.coresecurity.com/advisories/advantech-webAccess-stack-based-buffer-overflow
Date published: 2014-11-19
Date of last update: 2014-11-19
Vendors contacted: Advantech
Release mode: Coordinated release

2. Vulnerability Information

Class: Stack-based Buffer Overflow [CWE-121]
Impact: Code execution
Remotely Exploitable: No
Locally Exploitable: Yes
CVE Name: CVE-2014-8388

3. Vulnerability Description

   Advantech WebAccess [1] is a browser-based software package for
   human-machine interfaces HMI, and supervisory control and data
   acquisition SCADA.

   Advantech WebAccess is vulnerable to a Stack-based buffer overflow
   attack, which can be exploited by remote attackers to execute arbitrary
   code, by providing a malicious html file with specific parameters for an
   ActiveX component.

4. Vulnerable packages

   . WebAccess 7.2
   . Other versions are probably affected too, but they were not checked.

5. Vendor Information, Solutions and Workarounds

   Given that this is a client-side vulnerability, affected users
   should avoid opening untrusted '.html' files. Core Security also
   recommends those affected use third party software such as Sentinel [3]
   or EMET [2] that could help to prevent the exploitation of affected
   systems to some extent.

   Additionally the vendor released WebAccess v8 [4] where it has
   deleted the vulnerable file 'webeye.ocx' but if version upgrade is being
   performed, the vulnerable ocx file is not deleted at all, therefore we
   do not consider this a correct fix.

6. Credits

   This vulnerability was discovered and researched by Ricardo Narvaja
   from Core Security Consulting Services. The publication of this advisory
   was coordinated by Joaquin Rodriguez Varela from Core Advisories Team.

7. Technical Description / Proof of Concept Code

   This vulnerability is caused by a stack buffer overflow when parsing
   the ip_address parameter. A malicious third party could trigger
   execution of arbitrary code within the context of the application, or
   otherwise crash the whole application. This is caused because the
   application copies to the stack the string without checking its length.

/-----

document.vdoactx.Connect(ip_address, port_no);

-----/

/-----

0001C2AA 8B11 MOV EDX,DWORD PTR DS:[ECX]
0001C2AC 8A45 08 MOV AL,BYTE PTR SS:[EBP+8]
0001C2AF 8802 MOV BYTE PTR DS:[EDX],AL
0001C2B1 FF01 INC DWORD PTR DS:[ECX]
0001C2B3 0FB6C0 MOVZX EAX,AL
0001C2B6 EB 0B JMP SHORT 0001C2C3

-----/

8. Report Timeline
   . 2014-10-01:

   Initial notification sent to ICS-CERT informing of the vulnerability
   and requesting the vendor's contact information.

. 2014-10-01:

ICS-CERT informs that they will ask the vendor if they want to

coordinate directly with us or if they prefer to have ICS-CERT mediate.
They request the vulnerability report.

. 2014-10-01:

ICS-CERT informs that the vendor answered that they would like the

ICS-CERT to mediate the coordination of the advisory. They requested
again the vulnerability report.

. 2014-10-01:

We send the vulnerability detail, including technical description

and a PoC.

. 2014-10-09:

We request a status update on the reported vulnerability.

. 2014-10-20:

ICS-CERT informs that the vendor has patched WebAccess in version

8.0 and published it. This was done without informing us in order to
make a coordianted release. The ICS-CERT asks if we can test the fix.

. 2014-10-21:

We clearly state how we disagree with the uncoordinated published

fix. We began testing the fix.

. 2014-10-21:

We inform them that the "webeye.ocx" file (version 1.0.1.35) is

still present in the new version.

. 2014-10-27:

ICS-CERT informs us that the vendor has removed the vulnerable OCX

file from the new version but it doesn't remove it from previous
installations, making the new version still vulnerable.

. 2014-11-13:

We inform them that we will publish this advisory as user release on

Wednesday 19th of November.

. 2014-11-19:

Advisory CORE-2014-0010 published.

9. References

[1] http://webaccess.advantech.com/.
[2] http://support.microsoft.com/kb/2458544.
[3] https://github.com/CoreSecurity/sentinel.
[4] http://webaccess.advantech.com/webaccess_download.php?lang=eng.

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12. Disclaimer

    The contents of this advisory are copyright (c) 2014 Core Security
    and (c) 2014 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
    advisories team, which is available for download at
    http://www.coresecurity.com/files/attachments/core_security_advisories.asc.