CredSSP Flaw Exposes Pepperl+Fuchs HMI Devices to Attacks
18.7.18 securityweek  Attack  Vulnerebility

A vulnerability in the Credential Security Support Provider (CredSSP) authentication protocol has been found to impact several human-machine interface (HMI) products from Germany-based industrial automation firm Pepperl+Fuchs.

The flaw, tracked as CVE-18-0886, affects all supported versions of Windows and it was fixed by Microsoft with its March 18 Patch Tuesday updates.

The vulnerability was discovered by security firm Preempt, which has classified it as critical, but Microsoft, which believes exploitation is “less likely,” has assigned it only an “important” severity rating.

CredSSP processes authentication requests for applications such as the Remote Desktop Protocol (RDP) and Windows Remote Management (WinRM). A man-in-the-middle (MitM) attacker can exploit this vulnerability to remotely execute arbitrary code and move laterally within the targeted organization’s network.

Microsoft says any application using CredSSP for authentication could be vulnerable to this type of attack.

According to an advisory published by Germany’s CERT@VDE, an organization that focuses on industrial cybersecurity, CVE-18-0886 affects Pepperl+Fuchs’ VisuNet RM, VisuNet PC, and Box Thin Client BTC human-machine interface products.

“A successful vulnerability exploitation enables an attacker to execute arbitrary code and get access to sensitive data, e.g. passwords of the compromised system. The vulnerability allows the attacker to intercept the initial RDP connection between a client and a remote-server. Then an attacker can relay user credentials to a target system and thus get complete Man in the Middle control over a session. A stolen session can be abused to run arbitrary code or commands on the target server on behalf of the user,” CERT@VDE said in its advisory.

Pepperl+Fuchs has advised owners of devices running RM Shell 4 and RM Shell 5 HMI software to install the security patches provided by the company. Users of devices running Windows 7 or Windows 10 can patch the vulnerability by updating Windows.

The advisory from CERT@VDE says Preempt reported the vulnerabilities to Pepperl+Fuchs, but the security firm told SecurityWeek that it did not explicitly reach out to any ICS vendor.

“CredSSP is a broadly used protocol and we worked with Microsoft, since it was in their software that we found these vulnerabilities,” said Ajit Sancheti, co-founder and CEO at Preempt. “It is quite likely that Pepperl+Fuchs uses the MSFT version and hence may have been informed by them.”

Products from other ICS vendors are likely also affected by the CredSSP vulnerability, but to date no other company has published security advisories.