Software Engineering Institute

The ABB PCU400 application serves as a communication gateway between RTUs that use the IEC-870-5-104 protocol and the SCADA server. The diagnostic web application contains a software flaw which allows an attacker to gain full access on the PCU400 server by sending a specially crafted packet to the X87 web interface on TCP port 8087.

Note that this issue affects PCU400 installations running the IEC60870-5-101/104 protocol based on X87.

A remote attacker may be able to execute arbitrary code with the privileges of the account running the x87 application.

Upgrade or Patch
According to ABB:

This issue is corrected in version 3.5.5 of the x87 executable. To obtain a patch or upgrade software please contact your vendor. The x87 executable is considered obsolete in newer versions of the PCU 400 and should be replaced by the newer x88 or x89 executable where applicable.

Restrict Access
This diagnostic web application is designed to be used locally. Restrictions should be put in place to limit remote access. According to ABB:

Unless there is a specific reason, a host based filter like the built-in firewall in Windows XP should be activated for the port 8087, denying access to the web interface from a remote location.