How severe is CVE-2026-25823?

CVE-2026-25823 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-2026-25823 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-25823?

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-2026-25823 have an EU (EUVD) identifier?

Yes. CVE-2026-25823 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11715.

When was CVE-2026-25823 published?

CVE-2026-25823 was published on 2026-03-13 and last updated on 2026-06-17.

CVE-2026-25823

CVE-2026-25823 is a critical-severity vulnerability 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-121.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11715
Weakness: CWE-121
Published: 2026-03-13
Last modified: 2026-06-17

Description

HMS Networks Ewon Flexy with firmware before 15.0s4, Cosy+ with firmware 22.xx before 22.1s6, and Cosy+ with firmware 23.xx before 23.0s3 have a stack buffer overflow that leads to a Denial of Service, which can also be exploited to achieve Unauthenticated Remote Code Execution.

Frequently asked questions

What is CVE-2026-25823?: HMS Networks Ewon Flexy with firmware before 15.0s4, Cosy+ with firmware 22.xx before 22.1s6, and Cosy+ with firmware 23.xx before 23.0s3 have a stack buffer overflow that leads to a Denial of Service, which can also be exploited to achieve Unauthenticated Remote Code Execution.
How severe is CVE-2026-25823?: CVE-2026-25823 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-2026-25823 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-25823?: 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-2026-25823 have an EU (EUVD) identifier?: Yes. CVE-2026-25823 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11715.
When was CVE-2026-25823 published?: CVE-2026-25823 was published on 2026-03-13 and last updated on 2026-06-17.

References

Other CWE-121 (Stack-based Buffer Overflow) vulnerabilities

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CVE-2026-12846 — Critical (CVSS 10.0): GV-I/O Box 4E is a smart embedded device with 4 input and 4 relays output that can be controlled over Ethernet and…
CVE-2026-12485 — Critical (CVSS 10.0): GV-I/O Box 4E is a smart embedded device with 4 input and 4 relays output that can be controlled over Ethernet and…
CVE-2026-37541 — Critical (CVSS 10.0): Buffer overflow vulnerability in Open Vehicle Monitoring System 3 (OVMS3) 3.3.005. In canformat_gvret.cpp, the length…
CVE-2026-42996 — Critical (CVSS 10.0): JS8Call through 2.3.1 and JS8Call-improved before 3.0 have a stack-based buffer overflow via a radio transmission of…

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