CVE-2021-34596Network attack vector

Controller denial of service via uninitialized pointer read

Published Oct 26, 2021 · Updated Sep 16, 2024

Access of an uninitialized pointer in CODESYS V2 before 2.4.7.56 allows remote attackers to interrupt controller service with a crafted request. The runtime communication server reads an uninitialized pointer while processing the malformed request. Processing requires either no configured level 1 online password or prior controller authentication, and the reported consequence is limited to availability.

CVSS severity6.5
Medium
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access of an uninitialized pointer in CODESYS V2 before 2.4.7.56 allows remote attackers to interrupt controller service with a crafted request. The runtime communication server reads an uninitialized pointer while processing the malformed request. Processing requires either no configured level 1 online password or prior controller authentication, and the reported consequence is limited to availability.

The record

CVE
CVE-2021-34596
Published
Oct 26, 2021
Updated
Sep 16, 2024
Vendor
CODESYS GmbH
Product
CODESYS Development System V2.3
Classifications
CWE-824, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 26, 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=PLCWinNT <V2.4.7.56
  2. Affected versionversion=Runtime Toolkit 32 bit full <V2.4.7.56

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CODESYS GmbH · CODESYS Development System V2.3version=PLCWinNT <V2.4.7.56; version=Runtime Toolkit 32 bit full <V2.4.7.56

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.5CERT VDECVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NVDAV:N/AC:L/Au:S/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-824Access of Uninitialized Pointer
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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