How severe is CVE-2026-25818?

CVE-2026-25818 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 high, integrity high, and availability none.

Is CVE-2026-25818 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-25818?

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-2026-25818 have an EU (EUVD) identifier?

Yes. CVE-2026-25818 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11711.

When was CVE-2026-25818 published?

CVE-2026-25818 was published on 2026-03-13 and last updated on 2026-06-17.

CVE-2026-25818

CVE-2026-25818 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-315.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (4th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11711
Weakness: CWE-315
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 weak entropy for authentication cookies, allowing an attacker with a stolen session cookie to find the user password by brute-forcing an encryption parameter.

Frequently asked questions

What is CVE-2026-25818?: 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 weak entropy for authentication cookies, allowing an attacker with a stolen session cookie to find the user password by brute-forcing an encryption parameter.
How severe is CVE-2026-25818?: CVE-2026-25818 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 high, integrity high, and availability none.
Is CVE-2026-25818 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-25818?: 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-2026-25818 have an EU (EUVD) identifier?: Yes. CVE-2026-25818 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11711.
When was CVE-2026-25818 published?: CVE-2026-25818 was published on 2026-03-13 and last updated on 2026-06-17.

References

Other CWE-315 vulnerabilities

CVE-2024-41290 — High (CVSS 8.1): FlatPress CMS v1.3.1 1.3 was discovered to use insecure methods to store authentication data via the cookie's component.
CVE-2021-34564 — Medium (CVSS 5.5): Any cookie-stealing vulnerabilities within the application or browser would enable an attacker to steal the user's…

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