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Vulnerability record · CVE-2021-34595 · published 26 October 2021

CVE-2021-34595: Wago 750-823 firmware memory buffer overflow vulnerability

Wago · 750 823 Firmware

A crafted request with invalid offsets may cause an out-of-bounds read or write access in CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56, resulting in a denial-of-service condition or local memory overwrite.

8.1 CVSS 3.1 High EPSS 0.88% · top 42.5% CWE-823 · CWE-823CWE-119 · Memory buffer overflow
8.1CVSS 3.1 base score, v2 5.5
0.88%EPSS exploitation probability, 30 days
NoNot in CISA KEV
30Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

A crafted request with invalid offsets may cause an out-of-bounds read or write access in CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56, resulting in a denial-of-service condition or local memory overwrite.

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

Affected products

30 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=16878&token=e5644ec405590e66aefa62304cb8632df9fc9e9c&download Vendor Advisory
https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16878&token=e5644ec405590e66aefa62304cb8632df9fc9e9c&download Vendor 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-2022-31806Codesys plcwinnt insecure default initialization vulnerabilityIn CODESYS V2 PLCWinNT and Runtime Toolkit 32 in versions prior to V2.4.7.57 password protection is not enabled by default and there is no informatio…EPSS 1.2%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%

Source: NIST National Vulnerability Database (record CVE-2021-34595), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.