Advisory Details

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Advantech WebAccess Node. Authentication is not required to exploit this vulnerability.

The specific flaw exists within spchapi.exe, which is accessed through the 0x2711 IOCTL in the webvrpcs process. The issue results from the lack of proper validation of a user-supplied string before using it to execute a system call. An attacker can leverage this vulnerability to execute code in the context of Administrator.

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

02/06/19 – ZDI sent the vulnerability report to ICS-CERT
02/12/19 – ICS-CERT replied with tracking number
03/08/19 – ICS-CERT advised ZDI the vendor was working on a fix for some issues and provided a report, but also advised that this issue would not be fixed
03/13/19 – ZDI notified the vendor that the report will be published as 0-day on 03/28/19

-- 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.

• 2019-01-22 - Vulnerability reported to vendor
• 2019-03-28 - Coordinated public release of advisory