CVE-2021-22791

No known exploitation. EPSS puts it in the 56th percentile. A vendor fix is available.

CVSS 3.16.5Medium EPSS percentile56th0.8% chance in 30 days CISA KEVNot listedNo confirmed exploitation
No public exploit known FixVendor fixNo build named by the sources

Published 2021-09-02Updated 2026-05-29Sources: CVE.org, NVD, BDU

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

A CWE-787: Out-of-bounds Write vulnerability that could cause a Denial of Service on the Modicon PLC controller / simulator when updating the controller application with a specially crafted project file exists in Modicon M580 CPU (part numbers BMEP* and BMEH*, all versions), Modicon M340 CPU (part numbers BMXP34*, all versions), Modicon MC80 (part numbers BMKC80*, all versions), Modicon Momentum Ethernet CPU (part numbers 171CBU*, all versions), PLC Simulator for EcoStruxureª Control Expert, including all Unity Pro versions (former name of EcoStruxureª Control Expert, all versions), PLC Simulator for EcoStruxureª Process Expert including all HDCS versions (former name of EcoStruxureª Process Expert, all versions), Modicon Quantum CPU (part numbers 140CPU*, all versions), Modicon Premium CPU (part numbers TSXP5*, all versions).

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS56th

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.8% chance of exploitation activity in the next 30 days, which ranks it in the 56th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

6 events over 1757 days, from the signal feeds we watch.

2026-06-25OpenVAS check added
2026-05-29Patch availablerecord updated
2021-09-02Publishedweakness classified, att&ck mapped

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Scored 6.5 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required LowRequires basic user-level privileges
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

Confidentiality NoneNo confidentiality impact
Integrity NoneNo integrity impact
Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

CWE-787No name in the record

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Initial AccessT1190Exploit Public-Facing Applicationhigh confidence
Privilege EscalationT1068Exploitation for Privilege Escalationhigh confidence

Sources

References in the record

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