What is CVE-2021-34583?

CVE-2021-34583 is a high-severity vulnerability in Codesys, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2021-10-26.

How severe is CVE-2021-34583?

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

Buffer overflow in Codesys

CVE-2021-34583

Crafted web server requests may cause a heap-based buffer overflow and could therefore trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.

Vulnerability class: Buffer Overflow

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: 0.084 (94.8th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 94.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.084 · newest: 0.084 · change: 0.000

Affected products

Weakness classification (CWE)

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-2021-34583?: CVE-2021-34583 is a high-severity vulnerability in Codesys, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2021-10-26.
How severe is CVE-2021-34583?: High severity. CVSS v3 base score is 7.5 out of 10.