CVE-2021-21000Network attack vector

Runtime login interruption via unbounded connections

Published May 24, 2021 · Updated Sep 16, 2024

Resource exhaustion in WAGO PFC200 and Series 750 controllers allows remote attackers to interrupt the runtime login service. The CODESYS 2.3 runtime login service accepts crafted network packets and allocates connection resources without adequate limits or throttling. Network access to the controller is sufficient; exploitation prevents runtime logins, but no broader device shutdown is reported.

CVSS severity7.5
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in WAGO PFC200 and Series 750 controllers allows remote attackers to interrupt the runtime login service. The CODESYS 2.3 runtime login service accepts crafted network packets and allocates connection resources without adequate limits or throttling. Network access to the controller is sufficient; exploitation prevents runtime logins, but no broader device shutdown is reported.

The record

CVE
CVE-2021-21000
Published
May 24, 2021
Updated
Sep 16, 2024
Vendor
WAGO
Product
PFC200 Controller
Classifications
CWE-770, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=750-823 <=FW07
  2. Affected versionversion=750-829 <=FW14
  3. Affected versionversion=750-831/000-00x <=FW14
  4. Affected versionversion=750-832/000-00x <=FW06
  5. Affected versionversion=750-852 <=FW14
  6. Affected versionversion=750-862 <=FW07
  7. Affected versionversion=750-880/0xx-xxx <=FW15
  8. Affected versionversion=750-881 <=FW14
  9. Affected versionversion=750-882 <=FW14
  10. Affected versionversion=750-885/0xx-xxx <=FW14
  11. Affected versionversion=750-889 <=FW14
  12. Affected versionversion=750-890/0xx-xxx <=FW07
  13. Affected versionversion=750-891 <=FW07
  14. Affected versionversion=750-893 <=FW07

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

WAGO · PFC200 Controllerversion=750-823 <=FW07; version=750-829 <=FW14; version=750-831/000-00x <=FW14; version=750-832/000-00x <=FW06; version=750-852 <=FW14; version=750-862 <=FW07; version=750-880/0xx-xxx <=FW15; version=750-881 <=FW14; version=750-882 <=FW14; version=750-885/0xx-xxx <=FW14; version=750-889 <=FW14; version=750-890/0xx-xxx <=FW07; version=750-891 <=FW07; version=750-893 <=FW07
WAGO · Series 750 Ethernet Controllerversion=750-8202/xxx-xxx <03.06.19 (18); version=750-8203/xxx-xxx <03.06.19 (18); version=750-8204/xxx-xxx <03.06.19 (18); version=750-8206/xxx-xxx <03.06.19 (18); version=750-8207/xxx-xxx <03.06.19 (18); version=750-8208/xxx-xxx <03.06.19 (18); version=750-8210/xxx-xxx <03.06.19 (18); version=750-8211/xxx-xxx <03.06.19 (18); version=750-8212/xxx-xxx <03.06.19 (18); version=750-8213/xxx-xxx <03.06.19 (18); version=750-8214/xxx-xxx <03.06.19 (18); version=750-8216/xxx-xxx <03.06.19 (18); version=750-8217/xxx-xxx <03.06.19 (18)

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3CERT VDECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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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-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial 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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