How severe is CVE-2019-10121?

CVE-2019-10121 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2019-10121 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-10121?

CVE-2019-10121 primarily affects Eq-3 Ccu3 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-10121?

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-2019-10121 published?

CVE-2019-10121 was published on 2019-07-10 and last updated on 2026-06-17.

CVE-2019-10121

CVE-2019-10121 is a critical-severity vulnerability in Eq-3 Ccu3 Firmware with a CVSS 3.x base score of 9.8. 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-306.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 5% (91st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-306
Affected product: Eq-3 Ccu3 Firmware
Published: 2019-07-10
Last modified: 2026-06-17

Description

eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.15 use session IDs for authentication but lack authorization checks. An attacker can obtain a session ID via the user authentication dialogue, aka HMCCU-153. This leads to automatic login as admin.

Frequently asked questions

What is CVE-2019-10121?: eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.15 use session IDs for authentication but lack authorization checks. An attacker can obtain a session ID via the user authentication dialogue, aka HMCCU-153. This leads to automatic login as admin.
How severe is CVE-2019-10121?: CVE-2019-10121 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2019-10121 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-10121?: CVE-2019-10121 primarily affects Eq-3 Ccu3 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-10121?: 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-2019-10121 published?: CVE-2019-10121 was published on 2019-07-10 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:eq-3:ccu3_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:eq-3:ccu2_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Eq-3 Ccu3 Firmware

CVE-2020-12834 — Critical (CVSS 9.8): eQ-3 Homematic Central Control Unit (CCU)2 through 2.51.6 and CCU3 through 3.51.6 allow Remote Code Execution in the…
CVE-2019-10122 — Critical (CVSS 9.8): eQ-3 HomeMatic CCU2 devices before 2.41.9 and CCU3 devices before 3.43.16 have buffer overflows in the ReGa ise GmbH…
CVE-2019-10119 — Critical (CVSS 9.8): eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.16 use session IDs for authentication but lack…
CVE-2019-14473 — High (CVSS 8.8): eQ-3 Homematic CCU2 and CCU3 use session IDs for authentication but lack authorization checks. Consequently, a valid…
CVE-2019-10120 — High (CVSS 8.8): On eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.16, automatic login configuration (aka…
CVE-2019-14474 — High (CVSS 7.5): eQ-3 Homematic CCU3 3.47.15 and prior has Improper Input Validation in function 'Call()' of ReGa core logic process,…

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