CVE-2021-31886 Explained : Impact and Mitigation

A stack-based buffer overflow vulnerability has been identified in various Siemens products, leading to Denial-of-Service and Remote Code Execution. This CVE affects a range of Siemens devices including APOGEE and Desigo series.

Understanding CVE-2021-31886

This vulnerability, labeled as CWE-170: Improper Null Termination, stems from the FTP server's inadequate validation of the "USER" command length, allowing malicious actors to exploit it.

What is CVE-2021-31886?

The vulnerability in Siemens products allows attackers to trigger a stack-based buffer overflow by sending specifically crafted requests to the affected device's FTP server.

The Impact of CVE-2021-31886

With successful exploitation, threat actors can cause Denial-of-Service conditions and potentially execute malicious code remotely on the affected device.

Technical Details of CVE-2021-31886

The affected Siemens products include but are not limited to APOGEE MBC, APOGEE MEC, Desigo PXC series, Nucleus NET, Nucleus Source Code, and TALON TC series.

Vulnerability Description

FTP server's improper validation of the "USER" command length results in a stack-based buffer overflow, creating opportunities for malicious actions.

Affected Systems and Versions

Multiple Siemens products are affected, with specific versions susceptible to this vulnerability outlined such as APOGEE PXC Compact (< V3.5.4) and Desigo PXC22.1-E.D (>= V2.3 and < V6.30.016).

Exploitation Mechanism

Attackers can exploit this weakness by sending maliciously crafted requests to the FTP server, bypassing its length validation and leading to buffer overflow.

Mitigation and Prevention

To address CVE-2021-31886, it is crucial for Siemens users to take immediate and ongoing security measures to protect their systems.

Immediate Steps to Take

Organizations should apply patches provided by Siemens, restrict access to the affected devices, and monitor network traffic for any suspicious activity.

Long-Term Security Practices

Implement strict network segmentation, conduct regular security audits, and keep all systems up to date with the latest security patches and updates.

Patching and Updates

Siemens has released patches and security advisories related to this vulnerability for the affected products. Users are advised to apply these patches promptly to mitigate the risks associated with CVE-2021-31886.