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Modicon M221 Firmware CVE-2018-7789

HIGH
Improper Check for Unusual or Exceptional Conditions (CWE-754)
2018-08-29 cybersecurity@se.com
Authentication Bypass Schneider Electric Modicon M221 Firmware
7.5
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
CWE-754
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Unusual condition handling
Impact

CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.69%.
Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the high-severity affected system.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.7% exploitation probability (EPSS)

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AnalysisAI

An Improper Check for Unusual or Exceptional Conditions vulnerability exists in Schneider Electric's Modicon M221 product (all references, all versions prior to firmware V1.6.2.0). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-754. An Improper Check for Unusual or Exceptional Conditions vulnerability exists in Schneider Electric's Modicon M221 product (all references, all versions prior to firmware V1.6.2.0). The vulnerability allows unauthorized users to remotely reboot Modicon M221 using crafted programing protocol frames. Affected products include: Schneider-Electric Modicon M221 Firmware.

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Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

DescriptionCVE.org

An Improper Check for Unusual or Exceptional Conditions vulnerability exists in Schneider Electric's Modicon M221 product (all references, all versions prior to firmware V1.6.2.0). The vulnerability allows unauthorized users to remotely reboot Modicon M221 using crafted programing protocol frames.

Threat Intelligence Overview

EPSS Score
0.7%
Top 28% exploitable
Data Quality
4 sources
Confidence: Medium
NVD CVE.org EPSS VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.7%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)CVE.org

cpe:2.3:o:schneider-electric:modicon_m221_firmware:*:*:*:*:*:*:*:*

More in Modicon M221 Firmware

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An Information Management Error vulnerability exists in Schneider Electric's Modicon M221 product (all references, all v
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A CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') vulnerabili
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A Permissions, Privileges, and Access Control vulnerability exists in Schneider Electric's Modicon M221 product (all ref
CVE-2019-6820 HIGH
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A CWE-306: Missing Authentication for Critical Function vulnerability exists which could cause a modification of device

CVE-2018-7821 HIGH
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An Environment (CWE-2) vulnerability exists in SoMachine Basic, all versions, and Modicon M221(all references, all versi
CVE-2019-10953 HIGH
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ABB, Phoenix Contact, Schneider Electric, Siemens, WAGO - Programmable Logic Controllers, multiple versions. Rated high

CVE-2018-7792 HIGH
7.5 Aug 29

A Permissions, Privileges, and Access Control vulnerability exists in Schneider Electric's Modicon M221 product (all ref
CVE-2020-7566 HIGH
7.3 Nov 19

A CWE-334: Small Space of Random Values vulnerability exists in Modicon M221 (all references, all versions) that could a
CVE-2020-7565 HIGH
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A CWE-326: Inadequate Encryption Strength vulnerability exists in Modicon M221 (all references, all versions) that could
CVE-2020-7567 MEDIUM
5.7 Nov 19

A CWE-311: Missing Encryption of Sensitive Data vulnerability exists in Modicon M221 (all references, all versions) that
CVE-2020-28214 MEDIUM
5.5 Dec 11

A CWE-760: Use of a One-Way Hash with a Predictable Salt vulnerability exists in Modicon M221 (all references, all versi
CVE-2020-7568 MEDIUM
4.3 Nov 19

A CWE-200: Exposure of Sensitive Information to an Unauthorized Actor vulnerability exists in Modicon M221 (all referenc

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References

Advisories & patches
ADVISORY https://vuldb.com/vuln/123385 ADVISORY https://www.schneider-electric.com/en/download/document/SEVD-2018-233-01/ REF http://www.securityfocus.com/bid/105171 REF https://ics-cert.us-cert.gov/advisories/ICSA-18-240-02

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