WECON PLC Editor

1. EXECUTIVE SUMMARY

• CVSS v3 7.8
• ATTENTION: Low attack complexity
• Vendor: WECON
• Equipment: PLC Editor
• Vulnerabilities: Stack-based Buffer Overflow, Out-of-bounds Write

2. RISK EVALUATION

Successful exploitation of these vulnerabilities may allow arbitrary code execution.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following versions of PLC Editor ladder logic software are affected:

• PLC Editor: Versions 1.3.8 and prior

3.2 VULNERABILITY OVERVIEW

3.2.1    STACK-BASED BUFFER OVERFLOW CWE-121

The affected product is vulnerable to a stack-based buffer overflow while processing project files, which may allow an attacker to execute arbitrary code.

CVE-2021-42705 has been assigned to this vulnerability. A CVSS v3 base score of 7.8 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).

3.2.2    OUT-OF-BOUNDS WRITE CWE-787

The affected product is vulnerable to an out-of-bounds write while processing project files, which may allow an attacker to execute arbitrary code.

CVE-2021-42707 has been assigned to this vulnerability. A CVSS v3 base score of 7.8 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).

3.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing, Energy, Water and Wastewater Systems
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: China

3.4 RESEARCHER

Natnael Samson (@NattiSamson), working with Trend Micro’s Zero Day Initiative, reported these vulnerabilities to CISA.

4. MITIGATIONS

WECON has not responded to requests to work with CISA to mitigate these vulnerabilities. Users of these affected products are invited to contact WECON technical support for additional information.

CISA also recommends users take the following measures to protect themselves from social engineering attacks:

• Do not click web links or open unsolicited attachments in email messages.
• Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.
• Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks.

CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.



CISA also provides a section for control systems security recommended practices on the ICS webpage on us-cert.cisa.gov. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Additional mitigation guidance and recommended practices are publicly available on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.



Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to CISA for tracking and correlation against other incidents.

No known public exploits specifically target these vulnerabilities. These vulnerabilities are not exploitable remotely.