How severe is CVE-2021-27289?

CVE-2021-27289 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-2021-27289 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2021-27289?

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.

Does CVE-2021-27289 have an EU (EUVD) identifier?

Yes. CVE-2021-27289 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-14054.

When was CVE-2021-27289 published?

CVE-2021-27289 was published on 2025-04-15 and last updated on 2026-06-17.

CVE-2021-27289

CVE-2021-27289 is a critical-severity vulnerability 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-294.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 1% (52nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2021-14054
Weakness: CWE-294
Published: 2025-04-15
Last modified: 2026-06-17

Description

A replay attack vulnerability was discovered in a Zigbee smart home kit manufactured by Ksix (Zigbee Gateway Module = v1.0.3, Door Sensor = v1.0.7, Motion Sensor = v1.0.12), where the Zigbee anti-replay mechanism - based on the frame counter field - is improperly implemented. As a result, an attacker within wireless range can resend captured packets with a higher sequence number, which the devices incorrectly accept as legitimate messages. This allows spoofed commands to be injected without authentication, triggering false alerts and misleading the user through notifications in the mobile application used to monitor the network.

Frequently asked questions

What is CVE-2021-27289?: A replay attack vulnerability was discovered in a Zigbee smart home kit manufactured by Ksix (Zigbee Gateway Module = v1.0.3, Door Sensor = v1.0.7, Motion Sensor = v1.0.12), where the Zigbee anti-replay mechanism - based on the frame counter field - is improperly implemented. As a result, an attacker within wireless range can resend captured packets with a higher sequence number, which the devices incorrectly accept as legitimate messages. This allows spoofed commands to be injected without authentication, triggering false alerts and misleading the user through notifications in the mobile application used to monitor the network.
How severe is CVE-2021-27289?: CVE-2021-27289 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-2021-27289 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2021-27289?: 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.
Does CVE-2021-27289 have an EU (EUVD) identifier?: Yes. CVE-2021-27289 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-14054.
When was CVE-2021-27289 published?: CVE-2021-27289 was published on 2025-04-15 and last updated on 2026-06-17.

References

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

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