CVE-2021-34586Network attack vector

Remote web-server crash via crafted request

Published Oct 26, 2021 · Updated Sep 17, 2024

NULL pointer dereference in CODESYS V2 web server before 1.1.9.22 allows remote attackers to crash the service via crafted requests. CODESYS has not disclosed which request field or handler supplies the NULL pointer that the server dereferences. Versions before 1.1.9.20 are exposed despite user management; versions 1.1.9.20 and 1.1.9.21 process the request when user management is disabled or after authentication.

CVSS severity7.5
High
EPSS probability13.08%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

NULL pointer dereference in CODESYS V2 web server before 1.1.9.22 allows remote attackers to crash the service via crafted requests. CODESYS has not disclosed which request field or handler supplies the NULL pointer that the server dereferences. Versions before 1.1.9.20 are exposed despite user management; versions 1.1.9.20 and 1.1.9.21 process the request when user management is disabled or after authentication.

The record

CVE
CVE-2021-34586
Published
Oct 26, 2021
Updated
Sep 17, 2024
Vendor
CODESYS GmbH
Product
CODESYS Development System V2.3
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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=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

5.0NVDAV: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
7.5CODESYS GmbHCVSS:3.0/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo