Advisory Details

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Advantech WebAccess. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within nvA1Media.ocx. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a stack-based buffer. An attacker can leverage this vulnerability to execute arbitrary code under the context of the process.

This vulnerability is being disclosed publicly without a patch in accordance with the ZDI 120 day deadline.

11/08/2016, 11/09/2016, 11/10/2016 and 11/15/2016 - ZDI disclosed the reports, 44 in all, to ICS-CERT
11/09/2016 - The vendor acknowledged receipt of the report through ICS-CERT and ICS-CERT provided ICS-VU-714103
04/27/2017 - ICS-CERT notified ZDI these might be fixed in the latest version and asked would ZDI re-test
05/03/2017 - ZDI replied that we cannot do the testing for Advantech
ICS-CERT did not respond
06/23/2017 - ZDI wrote to ICS-CERT requesting any available update
07/31/2017 - ZDI wrote to ICS-CERT requesting any available update
08/01/2017 - ZDI wrote to ICS-CERT advising of the intent to 0-day

-- Mitigation:
Given the nature of the vulnerability, the only salient mitigation strategy is to restrict interaction with the service to trusted machines. Only the clients and servers that have a legitimate procedural relationship with the service should be permitted to communicate with it. This could be accomplished in a number of ways, most notably with firewall rules/whitelisting. These features are available in the native Windows Firewall, as described in http://technet.microsoft.com/en-us/library/cc725770%28WS.10%29.aspx and numerous other Microsoft Knowledge Base articles.

• 2016-11-08 - Vulnerability reported to vendor
• 2017-08-07 - Coordinated public release of advisory