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Vulnerability record · CVE-2021-34586 · published 26 October 2021

CVE-2021-34586: Wago 750-823 firmware null pointer dereference vulnerability

Wago · 750 823 Firmware

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.

7.5 CVSS 3.1 High EPSS 14% · top 3.6% CWE-476 · NULL pointer dereference
7.5CVSS 3.1 base score, v2 5.0
14%EPSS exploitation probability, 30 days
NoNot in CISA KEV
28Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

28 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16876&token=a3f1d937f95e7034879f4f2ea8e5a99b168256a7&download Vendor Advisory
https://www.tenable.com/security/research/tra-2021-47 ExploitThird Party Advisory
https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16876&token=a3f1d937f95e7034879f4f2ea8e5a99b168256a7&download Vendor Advisory
https://www.tenable.com/security/research/tra-2021-47 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2021-34569Wago 750-8100 firmware out-of-bounds write vulnerabilityIn WAGO I/O-Check Service in multiple products an attacker can send a specially crafted packet containing OS commands to crash the diagnostic tool an…EPSS 0.86%9.8CVE-2021-30188Wago 750-893 firmware out-of-bounds write vulnerabilityCODESYS V2 runtime system SP before 2.4.7.55 has a Stack-based Buffer Overflow.EPSS 1.3%9.8CVE-2021-30189Wago 750-893 firmware out-of-bounds write vulnerabilityCODESYS V2 Web-Server before 1.1.9.20 has a Stack-based Buffer Overflow.EPSS 1.3%9.8CVE-2021-30190Wago 750-893 firmware missing authentication for critical function vulnerabilityCODESYS V2 Web-Server before 1.1.9.20 has Improper Access Control.EPSS 1.4%9.8CVE-2021-30192Wago 750-893 firmware vulnerabilityCODESYS V2 Web-Server before 1.1.9.20 has an Improperly Implemented Security Check.EPSS 1.2%9.8CVE-2021-30193Wago 750-893 firmware out-of-bounds write vulnerabilityCODESYS V2 Web-Server before 1.1.9.20 has an Out-of-bounds Write.EPSS 1.2%9.8CVE-2019-16265Codesys eni server out-of-bounds write vulnerabilityCODESYS V2.3 ENI server up to V3.2.2.24 has a Buffer Overflow.EPSS 1.6%9.1CVE-2021-34566Wago 750-8100 firmware classic buffer overflow vulnerabilityIn WAGO I/O-Check Service in multiple products an unauthenticated remote attacker can send a specially crafted packet containing OS commands to crash…EPSS 1.1%

Source: NIST National Vulnerability Database (record CVE-2021-34586), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.