How severe is CVE-2026-34021?

CVE-2026-34021 has a CVSS 4.0 base score of 8.6, rated high severity.

Is CVE-2026-34021 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-34021?

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.

Does CVE-2026-34021 have an EU (EUVD) identifier?

Yes. CVE-2026-34021 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-36704.

When was CVE-2026-34021 published?

CVE-2026-34021 was published on 2026-06-15 and last updated on 2026-06-17.

CVE-2026-34021

CVE-2026-34021 is a high-severity vulnerability with a CVSS 4.0 base score of 8.6. 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-294.

Key facts

Severity: High (CVSS 4.0 base score 8.6)
EPSS exploit prediction: 0% (10th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-36704
Weakness: CWE-294
Published: 2026-06-15
Last modified: 2026-06-17

Description

The Wertheim SafeController 5400, Controller 5400 - AssemblyVersion 6.11.8130.22320, uses RS-485 communication between the server and the microcontroller without cryptographic protection. An attacker with access to the communication path between the server and the microcontroller can sniff RS-485 messages and replay previously observed messages. This can be used, for example, to spoof a "quit alarm" message and continuously deactivate the safe alarm.

Frequently asked questions

What is CVE-2026-34021?: The Wertheim SafeController 5400, Controller 5400 - AssemblyVersion 6.11.8130.22320, uses RS-485 communication between the server and the microcontroller without cryptographic protection. An attacker with access to the communication path between the server and the microcontroller can sniff RS-485 messages and replay previously observed messages. This can be used, for example, to spoof a "quit alarm" message and continuously deactivate the safe alarm.
How severe is CVE-2026-34021?: CVE-2026-34021 has a CVSS 4.0 base score of 8.6, rated high severity.
Is CVE-2026-34021 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-34021?: 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.
Does CVE-2026-34021 have an EU (EUVD) identifier?: Yes. CVE-2026-34021 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-36704.
When was CVE-2026-34021 published?: CVE-2026-34021 was published on 2026-06-15 and last updated on 2026-06-17.

References

Other CWE-294 (Authentication Bypass by Capture-replay) vulnerabilities

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