CVE-2021-21000

CVE-2021-21000 is a medium-severity vulnerability in Wago 750-823 Firmware with a CVSS 3.x base score of 5.3. 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-770.

Key facts

• Severity: Medium (CVSS 3.x base score 5.3)
• CVSS v2: 5.0
• EPSS exploit prediction: 1% (60th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-770
• Affected product: Wago 750-823 Firmware
• Published: 2021-05-24
• Last modified: 2026-06-17

Description

On WAGO PFC200 devices in different firmware versions with special crafted packets an attacker with network access to the device could cause a denial of service for the login service of the runtime.

Frequently asked questions

What is CVE-2021-21000?

On WAGO PFC200 devices in different firmware versions with special crafted packets an attacker with network access to the device could cause a denial of service for the login service of the runtime.

How severe is CVE-2021-21000?

CVE-2021-21000 has a CVSS 3.x base score of 5.3, rated medium 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 low.

Is CVE-2021-21000 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-2021-21000?

CVE-2021-21000 primarily affects Wago 750-823 Firmware. In total, 27 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21000?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21000 published?

CVE-2021-21000 was published on 2021-05-24 and last updated on 2026-06-17.

References

• https://cert.vde.com/en-us/advisories/vde-2021-014

Affected products (27)

• cpe:2.3:o:wago:750-823_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-829_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-831_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-832_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-852_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-862_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-880_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-881_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-882_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-885_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-889_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-890_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-891_firmware:*:*:*:*:*:*:*:*
• cpe:2.3:o:wago:750-893_firmware:*:*:*:*:*:*:*:*
• 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:*:*:*:*:*:*:*:*

More vulnerabilities in Wago 750-823 Firmware

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• CVE-2021-30192 — Critical (CVSS 9.8): CODESYS V2 Web-Server before 1.1.9.20 has an Improperly Implemented Security Check.
• CVE-2021-30190 — Critical (CVSS 9.8): CODESYS V2 Web-Server before 1.1.9.20 has Improper Access Control.
• CVE-2021-30189 — Critical (CVSS 9.8): CODESYS V2 Web-Server before 1.1.9.20 has a Stack-based Buffer Overflow.
• CVE-2021-30188 — Critical (CVSS 9.8): CODESYS V2 runtime system SP before 2.4.7.55 has a Stack-based Buffer Overflow.

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