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Siemens updated a fix to a vulnerability in devices using the PROFINET Discovery and Configuration Protocol (DCP) that could cause a denial of service (DoS), according to a report with ICS-CERT.

An attacker may be able to cause a DoS condition requiring a manual restart by exploiting this vulnerability.

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Duan JinTong, Ma ShaoShuai, and Cheng Lei from NSFOCUS Security Team reported this vulnerability directly to Siemens. The vulnerability is exploitable from an adjacent network.

Siemens said the vulnerability affects the following products using the PROFINET DCP:
• SIMATIC WinCC (TIA Portal)
V13: All versions prior to V13 SP2
V14: All versions prior to V14 SP1
V13: All versions prior to V13 SP2
V14: All versions prior to V14 SP1
• SIMATIC STEP 7 V5.X: All versions prior to V5.6
• STEP 7 – Micro/WIN SMART: All versions
• SMART PC Access V2.0
• SIMATIC Automation Tool: All versions
• SIMATIC WinCC: All versions prior to V7.4 SP1 Upd1
• SIMATIC PCS 7: All versions
• SIMATIC NET PC-Software: All versions
• Primary Setup Tool (PST): All versions
• Security Configuration Tool (SCT): All versions prior to V5.0
• SINEMA Server: All versions
• SINAUT ST7CC: All versions
• SIMATIC WinAC RTX 2010 SP2: All versions
• SIMATIC WinAC RTX F 2010 SP2: All versions
• SINUMERIK 808D Programming Tool: All versions
• SIMATIC WinCC flexible 2008: All versions

Schneider Bold

Specially crafted PROFINET DCP broadcast packets sent to the affected products on a local Ethernet segment (Layer 2) could cause a DoS condition in some services. The services may require manual restart to recover.

CVE-2017-6865 is the case number assigned to this vulnerability, which has a CVSS v3 base score of 6.5.

The product sees action in the critical manufacturing, food and agriculture, chemical, energy, and water and wastewater system sectors. They also see use on a global basis.

No known public exploits specifically target this vulnerability. However, it would take an attacker with low skill level to leverage the vulnerability.

Siemens provides updates that fix the vulnerability for the following affected products and recommends users update to the new fixed version:
• SIMATIC WinCC (TIA Portal) V13: Update to V13 SP2
• SIMATIC WinCC (TIA Portal) V14: Update to V14 SP1
• SIMATIC STEP 7 (TIA Portal) V13: Update to V13 SP2
• SIMATIC STEP 7 (TIA Portal) V14: Update to V14 SP1
• SIMATIC STEP 7 V5.X:  Upgrade to V5.6
• SIMATIC WinCC:  Update to V7.4 SP1 Upd1
• Security Configuration Tool (SCT):  Update to V5.0

The affected component is shared among all of the affected products on the host. Installing one fixed version will mitigate the vulnerability for all Siemens applications installed on that host.

Siemens is preparing updates for the remaining affected products and recommends the following mitigations in the meantime:
• Apply cell protection concept
• Use VPN for protecting network communication between cells
• Apply Defense-in-Depth

As a general security measure, Siemens recommends protecting industrial control systems networks with appropriate mechanisms. Siemens advises configuring the environment according to Siemens operational guidelines in order to run the devices in a protected IT environment.

For more information on this vulnerability and more detailed mitigation instructions, see Siemens Security Advisory SSA-275839.

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