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 tv_enua.exe, which is accessed through the 0x2711 IOCTL in the webvrpcs process. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. 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 ZDI policies.

02/04/19 – ZDI sent the vulnerability reports to ICS-CERT
02/04/19 – ICS-CERT replied with tracking number
02/18/19 – ICS-CERT advised ZDI the vendor was working on a fix for some issues and provided a reports, but also advised that 2 issues would not be fixed
02/18/19 – ZDI replied and asked if the vendor was working with the upstream vendor and ICS-CERT agreed to request clarification
02/19/19 – ICS-CERT conveyed the vendor’s reply:
“These two installer is already install successfully after installing WebAccess/SCADA installer package. We think these won’t be damage on system so we will ignore these two cases.”
02/21/19 – ZDI notified the vendor if these are not patched that the reports will be published as 0-day on 02/28/19

-- 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.

• 2019-02-04 - Vulnerability reported to vendor
• 2019-02-28 - Coordinated public release of advisory
• 2019-05-30 - Advisory Updated