CVE-2026-25818
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedHMS 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceHMS Networks Ewon Flexy and Cosy+ devices contain weak entropy in authentication cookie generation. An attacker who obtains a stolen session cookie can brute-force the encryption parameter to recover user passwords, effectively allowing full account takeover.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the Ewon device modelAccess the device web interface and locate the device information page, or inspect a device configuration backup file for the model name (Flexy or Cosy+)Affected if The device is an Ewon Flexy or Cosy+ product
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Determine the installed firmware versionCheck the device web interface System > Information page, or look for the firmware version string in a configuration backup fileAffected if The firmware version cannot be determined or is not visible
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Compare Flexy firmware to vulnerable rangeIf the device is a Flexy, compare your installed version against versions prior to 15.0s4 (e.g., 15.0s0-s3, earlier major versions)Affected if Flexy firmware version is below 15.0s4
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Compare Cosy+ 22.xx firmware to vulnerable rangeIf the device is a Cosy+ running 22.xx firmware, compare your version against versions prior to 22.1s6Affected if Cosy+ 22.xx firmware version is below 22.1s6
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Compare Cosy+ 23.xx firmware to vulnerable rangeIf the device is a Cosy+ running 23.xx firmware, compare your version against versions prior to 23.0s3Affected if Cosy+ 23.xx firmware version is below 23.0s3
The device is affected if it is an Ewon Flexy or Cosy+ running firmware version below the fixed releases (15.0s4 for Flexy, 22.1s6 for Cosy+ 22.xx, 23.0s3 for Cosy+ 23.xx).
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpdate affected devices to firmware versions 15.0s4 (Flexy), 22.1s6 (Cosy+ 22.xx), or 23.0s3 (Cosy+ 23.xx) or later to resolve the weak entropy issue.
Ewon Flexy: firmware 15.0s4 or later; Cosy+ 22.xx: firmware 22.1s6 or later; Cosy+ 23.xx: firmware 23.0s3 or later
- Identify the specific HMS Networks device model (Ewon Flexy or Cosy+)
- Check the current firmware version on the device via the device web interface or HMS configuration tools
- Download the appropriate fixed firmware from HMS Networks official support portal
- Follow HMS Networks official firmware update procedure to apply the upgrade: For Flexy upgrade to 15.0s4 or later, For Cosy+ 22.xx upgrade to 22.1s6 or later, For Cosy+ 23.xx upgrade to 23.0s3 or later
- After upgrade, verify the firmware version and test authentication functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-25818 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-25818 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data