CVE-2018-16561 Explained : Impact and Mitigation

A security flaw has been discovered in SIMATIC S7-300 CPUs (Versions below V3.X.16) that could lead to a Denial-of-Service situation due to inadequate verification of S7 communication packets.

Understanding CVE-2018-16561

What is CVE-2018-16561?

This CVE identifies a vulnerability in SIMATIC S7-300 CPUs where specially manipulated S7 communication packets can cause a CPU malfunction, resulting in a Denial-of-Service scenario.

The Impact of CVE-2018-16561

Exploiting this vulnerability could disrupt the core functionality of the CPU, compromising the overall availability of the system. No instances of exploitation were known at the time of the advisory publication.

Technical Details of CVE-2018-16561

Vulnerability Description

Affected CPUs inadequately verify S7 communication packets, leading to a potential Denial-of-Service situation.
The CPU remains inactive until manually restarted after exploitation.

Affected Systems and Versions

Product: SIMATIC S7-300 CPUs
Vendor: Siemens
Versions: All versions < V3.X.16

Exploitation Mechanism

Attacker needs to send a specially manipulated S7 communication packet to the CPU's communication interface (Ethernet, PROFIBUS, MPI).
No user interaction or privileges are required for exploitation.

Mitigation and Prevention

Immediate Steps to Take

Apply vendor-provided mitigations to address the vulnerability.
Monitor for any unusual CPU behavior that could indicate exploitation.

Long-Term Security Practices

Regularly update firmware and security patches for the affected systems.

Patching and Updates

Stay informed about security advisories and updates from Siemens to patch the vulnerability.