How severe is CVE-2021-34566?

CVE-2021-34566 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2021-34566 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34566?

CVE-2021-34566 primarily affects Wago 750-8100 Firmware. In total, 196 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34566?

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

When was CVE-2021-34566 published?

CVE-2021-34566 was published on 2022-11-09 and last updated on 2026-06-17.

CVE-2021-34566

CVE-2021-34566 is a critical-severity vulnerability in Wago 750-8100 Firmware with a CVSS 3.x base score of 9.1. 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Wago 750-8100 Firmware
Published: 2022-11-09
Last modified: 2026-06-17

Description

In WAGO I/O-Check Service in multiple products an unauthenticated remote attacker can send a specially crafted packet containing OS commands to crash the iocheck process and write memory resulting in loss of integrity and DoS.

Frequently asked questions

What is CVE-2021-34566?: In WAGO I/O-Check Service in multiple products an unauthenticated remote attacker can send a specially crafted packet containing OS commands to crash the iocheck process and write memory resulting in loss of integrity and DoS.
How severe is CVE-2021-34566?: CVE-2021-34566 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2021-34566 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34566?: CVE-2021-34566 primarily affects Wago 750-8100 Firmware. In total, 196 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34566?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-34566 published?: CVE-2021-34566 was published on 2022-11-09 and last updated on 2026-06-17.

References

https://cert.vde.com/en/advisories/VDE-2020-036/

Affected products (196)

cpe:2.3:o:wago:750-8100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8100_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8100_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8100_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101\/025-000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101\/025-000_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101\/025-000_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8101\/025-000_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102\/025-000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102\/025-000_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102\/025-000_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8102\/025-000_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-011_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-011_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-011_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-011_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-012_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-012_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-012_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-012_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-022_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-022_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-022_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/000-022_firmware:18:patch_2:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/025-000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/025-000_firmware:18:-:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/025-000_firmware:18:patch_1:*:*:*:*:*:*
cpe:2.3:o:wago:750-8202\/025-000_firmware:18:patch_2:*:*:*:*:*:*

More vulnerabilities in Wago 750-8100 Firmware

CVE-2021-34569 — Critical (CVSS 9.8): In WAGO I/O-Check Service in multiple products an attacker can send a specially crafted packet containing OS commands…
CVE-2021-34567 — High (CVSS 8.2): In WAGO I/O-Check Service in multiple products an unauthenticated remote attacker can send a specially crafted packet…
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