CVE-2021-22764Network attack vector

Unauthenticated Modbus TCP interruption via crafted HTTP request

Published Jun 11, 2021 · Updated May 29, 2026

Improper authentication in Schneider Electric PowerLogic PM55xx, PM8ECC, EGX100, and EGX300 allows remote attackers to interrupt Modbus TCP. Schneider Electric has not disclosed which HTTP request handler omits authentication or how the crafted request disables the Modbus TCP service. The interface is reachable over the network without credentials, and successful exploitation causes a connectivity loss rather than data disclosure or device takeover.

CVSS severity5.3
Medium
EPSS probability1.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Schneider Electric PowerLogic PM55xx, PM8ECC, EGX100, and EGX300 allows remote attackers to interrupt Modbus TCP. Schneider Electric has not disclosed which HTTP request handler omits authentication or how the crafted request disables the Modbus TCP service. The interface is reachable over the network without credentials, and successful exploitation causes a connectivity loss rather than data disclosure or device takeover.

The record

CVE
CVE-2021-22764
Published
Jun 11, 2021
Updated
May 29, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-287, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 2021CVE publishedPublication date reported by the CVE source.
  2. May 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.3Schneider ElectricCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T0814Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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