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CVE-2020-7533VulnerabilityPublished Updated

CVE-2020-7533: Web Server on Modicon M340, Modicon Quantum and Modicon Premium Legacy offers and their Communication Modules (see security notification for version information) · Improper Authentication

Affects Web Server on Modicon M340, Modicon Quantum and Modicon Premium Legacy offers and their Communication Modules (see security notification for version information)Source CVE Database V5

0

Not known to be exploited.

Data as of 26 Oct 2026, 08:30 UTC

Severity
Low

Rated Low by the CNA (schneider) · No CVSS score from NVD or the CNA

EPSS
2.3% chance of exploitation in 30 days – higher than 83% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Dec 2020

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

AI-suggested

European organizations using Modicon M340, Quantum, or Premium legacy PLCs should immediately review their deployment of these devices and implement compensating controls. Specific mitigations include: 1) Isolate affected PLCs and their communication modules from untrusted networks, especially the internet, using network segmentation and firewalls. 2) Restrict access to the web server interfaces to trusted management networks only, employing strict access control lists (ACLs). 3) Monitor network traffic for unusual HTTP requests targeting the PLC web servers that could indicate exploitation attempts. 5) Employ intrusion detection systems (IDS) or anomaly detection tailored for OT environments to detect unauthorized command execution attempts. 6) Conduct regular security audits and penetration testing focused on OT assets to identify and remediate similar authentication weaknesses. 7) Implement multi-factor authentication (MFA) and strong password policies on management interfaces where possible to reduce risk of unauthorized access. 8) Maintain up-to-date asset inventories and ensure that legacy devices are replaced or upgraded as part of long-term cybersecurity strategies.

Description

CWE-287: Improper Authentication vulnerability exists which could cause the execution of commands on the webserver without authentication when sending specially crafted HTTP requests.

References

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