What is CVE-2021-34586?

CVE-2021-34586 is a high-severity vulnerability in Codesys, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2021-10-26.

How severe is CVE-2021-34586?

High severity. CVSS v3 base score is 7.5 out of 10.

NULL pointer dereference in Codesys

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.

Published 2021-10-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.141 (96.5th percentile), scored 2026-09-30.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 96th percentile — 96.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.131 · newest: 0.141 · change: +0.010

Affected products

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

customers.codesys.com/index.php (Vendor Advisory)
www.tenable.com/security/research/tra-2021-47 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-34586?: CVE-2021-34586 is a high-severity vulnerability in Codesys, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2021-10-26.
How severe is CVE-2021-34586?: High severity. CVSS v3 base score is 7.5 out of 10.