How severe is CVE-2021-34593?

CVE-2021-34593 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-34593 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34593?

CVE-2021-34593 primarily affects Codesys Plcwinnt. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34593?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-34593 published?

CVE-2021-34593 was published on 2021-10-26 and last updated on 2026-06-17.

CVE-2021-34593

CVE-2021-34593 is a high-severity vulnerability in Codesys Plcwinnt with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (84th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Codesys Plcwinnt
Published: 2021-10-26
Last modified: 2026-06-17

Description

In CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56 unauthenticated crafted invalid requests may result in several denial-of-service conditions. Running PLC programs may be stopped, memory may be leaked, or further communication clients may be blocked from accessing the PLC.

Frequently asked questions

What is CVE-2021-34593?: In CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56 unauthenticated crafted invalid requests may result in several denial-of-service conditions. Running PLC programs may be stopped, memory may be leaked, or further communication clients may be blocked from accessing the PLC.
How severe is CVE-2021-34593?: CVE-2021-34593 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-34593 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34593?: CVE-2021-34593 primarily affects Codesys Plcwinnt. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34593?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-34593 published?: CVE-2021-34593 was published on 2021-10-26 and last updated on 2026-06-17.

References

Affected products (15)

cpe:2.3:o:wago:750-8202_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8203_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8204_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8206_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8207_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8208_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8210_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8211_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8212_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8213_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8214_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8216_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8217_firmware:*:*:*:*:*:*:*:*
cpe:2.3:a:codesys:plcwinnt:*:*:*:*:*:*:*:*
cpe:2.3:a:codesys:runtime_toolkit:*:*:*:*:*:*:x86:*

More vulnerabilities in Codesys Plcwinnt

CVE-2022-31806 — Critical (CVSS 9.8): In CODESYS V2 PLCWinNT and Runtime Toolkit 32 in versions prior to V2.4.7.57 password protection is not enabled by…
CVE-2022-32143 — High (CVSS 8.8): In multiple CODESYS products, file download and upload function allows access to internal files in the working…
CVE-2022-32138 — High (CVSS 8.8): In multiple CODESYS products, a remote attacker may craft a request which may cause an unexpected sign extension,…
CVE-2022-32137 — High (CVSS 8.8): In multiple CODESYS products, a low privileged remote attacker may craft a request, which may cause a heap-based buffer…
CVE-2022-32142 — High (CVSS 8.1): Multiple CODESYS Products are prone to a out-of bounds read or write access. A low privileged remote attacker may craft…
CVE-2022-1965 — High (CVSS 8.1): Multiple products of CODESYS implement a improper error handling. A low privilege remote attacker may craft a request,…

All CVEs affecting Codesys Plcwinnt →

Other CWE-755 (Improper Handling of Exceptional Conditions) vulnerabilities

CVE-2025-34193 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) Virtual Appliance Host versions prior to 25.1.102 and Application versions prior…
CVE-2025-10156 — Critical (CVSS 9.8): An Improper Handling of Exceptional Conditions vulnerability in the ZIP archive scanning component of mmaitre314…
CVE-2021-42142 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. DTLS servers mishandle the early use of a…
CVE-2021-42141 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through 2018-08-30. One incorrect handshake could complete with…
CVE-2023-38406 — Critical (CVSS 9.8): bgpd/bgp_flowspec.c in FRRouting (FRR) before 8.4.3 mishandles an nlri length of zero, aka a "flowspec overflow."
CVE-2022-23121 — Critical (CVSS 9.8): This vulnerability allows remote attackers to execute arbitrary code on affected installations of Netatalk.…

Browse all CWE-755 (Improper Handling of Exceptional Conditions) vulnerabilities →