CVE-2021-34585Network attack vector

Remote service crash via unchecked parser result

Published Oct 26, 2021 · Updated Sep 16, 2024

Unchecked return value in the CODESYS V2 web server in CODESYS Development System V2.3 before 2.3.9.68 allows remote attackers to crash it. The request parser can return an error, but the web server does not check that result under all conditions and dereferences an invalid address. Versions before web server 1.1.9.20 accept the request without authentication; later affected versions require authentication only when WebVisu user management is enabled.

CVSS severity7.5
High
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unchecked return value in the CODESYS V2 web server in CODESYS Development System V2.3 before 2.3.9.68 allows remote attackers to crash it. The request parser can return an error, but the web server does not check that result under all conditions and dereferences an invalid address. Versions before web server 1.1.9.20 accept the request without authentication; later affected versions require authentication only when WebVisu user management is enabled.

The record

CVE
CVE-2021-34585
Published
Oct 26, 2021
Updated
Sep 16, 2024
Vendor
CODESYS GmbH
Product
CODESYS Development System V2.3
Classifications
CWE-252, T0814
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

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Is a vulnerable build present?

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

  1. Affected versionversion=all web servers <V1.1.9.22

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CODESYS GmbH · CODESYS Development System V2.3version=all web servers <V1.1.9.22

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5CERT@VDECVSS: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-252Unchecked Return Value
T0814Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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