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No exploitation reportedFix available

CVE-2021-34586

No exploitation reported by the sources we read.

  • Published2021-10-26
  • Fixed in1.1.9.22
  • WeaknessCWE-476

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In the CODESYS V2 web server prior to V1.1.9.22 crafted web server requests may cause a Null pointer dereference in the CODESYS web server and may result in a denial-of-service condition.

Timeline

dates in UTC
  1. 2021-10-2610:15CVE publishedNVD

Versions per branch

NVD
Codesys
BranchAffectedFixed in
1.1< 1.1.9.221.1.9.22
Wago 750-8202 firmwareversion to verify
BranchAffectedFixed in
—< fw20fw20
Wago 750-8203 firmwareversion to verify
BranchAffectedFixed in
—< fw20fw20

25 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Codesys to 1.1.9.22

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.17.5known since 2026-10-23
  • NVDCVSS 3.17.5read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • CNAweakness (CWE)CWE-476known since 2026-10-23
  • NVDweakness (CWE)CWE-476read 2026-10-23
  • FIRST EPSSEPSS score13.7 %read 2026-11-09
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2021-10-26
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-hmwx-8xfx-mg6m

Frequently asked questions

What is CVE-2021-34586?

In the CODESYS V2 web server prior to V1.1.9.22 crafted web server requests may cause a Null pointer dereference in the CODESYS web server and may result in a denial-of-service condition.

Is CVE-2021-34586 actively exploited?

Active exploitation of CVE-2021-34586 has not been confirmed. Its EPSS score was 13.7% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-34586?

CVE-2021-34586 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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