CVE-2020-27736 Explained : Impact and Mitigation

A vulnerability has been identified in various Siemens products, allowing attackers to cause denial-of-service conditions or leak memory.

Understanding CVE-2020-27736

This CVE involves a vulnerability in Siemens products due to improper null termination, potentially leading to memory leaks or denial-of-service attacks.

What is CVE-2020-27736?

The DNS domain name label parsing functionality in affected Siemens products does not properly validate null-terminated names in DNS responses, allowing attackers to exploit this issue.

The Impact of CVE-2020-27736

The parsing of malformed responses could result in a read past the end of an allocated structure, enabling attackers with network privileges to cause denial-of-service conditions or leak memory.

Technical Details of CVE-2020-27736

This section provides more technical insights into the vulnerability.

Vulnerability Description

The vulnerability arises from the improper null termination in DNS domain name label parsing, leading to potential memory leaks or denial-of-service attacks.

Affected Systems and Versions

APOGEE PXC Compact (BACnet) (All versions < V3.5.5)
APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20)
APOGEE PXC Modular (BACnet) (All versions < V3.5.5)
APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20)
Nucleus NET (All versions)
Nucleus ReadyStart V3 (All versions < V2017.02.3)
Nucleus ReadyStart V4 (All versions < V4.1.0)
Nucleus Source Code (Versions including affected DNS modules)
SIMOTICS CONNECT 400 (All versions < V0.5.0.0)
TALON TC Compact (BACnet) (All versions < V3.5.5)
TALON TC Modular (BACnet) (All versions < V3.5.5)

Exploitation Mechanism

The vulnerability allows attackers to exploit the DNS domain name label parsing functionality, potentially causing a denial-of-service condition or memory leak.

Mitigation and Prevention

Protect your systems from CVE-2020-27736 with these mitigation strategies.

Immediate Steps to Take

Apply patches provided by Siemens to address the vulnerability.
Monitor network traffic for any signs of exploitation.
Restrict network access to vulnerable systems.

Long-Term Security Practices

Regularly update and patch all software and firmware.
Conduct security assessments and audits to identify vulnerabilities.
Implement network segmentation to limit the impact of potential attacks.

Patching and Updates

Ensure that all affected Siemens products are updated to versions that address the CVE-2020-27736 vulnerability.