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Extremeguest EssentialsApplication · Extremenetworks

CVE-2025-8679

CRITICAL · 9.8 CVSS v3.1 Published 2025-10-01
Fix available
A fix is available. Upgrade to 25.5.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
In ExtremeGuest Essentials before 25.5.0, captive-portal may permit unauthorized access via manual brute-force procedure. Under certain ExtremeGuest Essentials captive-portal SSID configurations, repeated manual login attempts may allow an unauthenticated device to be marked as authenticated and obtain network access. Client360 logs may display the client MAC as the username despite no MAC-authentication being enabled.

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 · moderate confidence

In ExtremeGuest Essentials before version 25.5.0, the captive-portal contains a logic flaw that allows an unauthenticated attacker to gain unauthorized network access through repeated manual login attempts. Under certain SSID configurations, the repeated attempts can eventually mark the device as authenticated, effectively bypassing authentication controls. The vulnerability is exacerbated by Client360 logs incorrectly displaying the client MAC as the username even without MAC-authentication enabled, obscuring the attack.

MitigationUpgrade ExtremeGuest Essentials to version 25.5.0 or later to remediate this vulnerability. Until the upgrade can be applied, consider disabling the affected captive-portal SSIDs or implementing additional network-level access controls to mitigate unauthorized access.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Extremeguest EssentialsApplication
Affected:< 25.5.0

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
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Confirm ExtremeGuest Essentials is deployed
    Locate the ExtremeGuest Essentials installation in your environment - this may be a physical appliance, virtual machine, or cloud deployment. Check the system information or admin interface for the product name.
    Affected if ExtremeGuest Essentials is present in your environment
  2. Identify installed version
    Access the ExtremeGuest Essentials admin interface or CLI and retrieve the current software version. This is typically found in System > About, System Info, or via 'show version' command.
    Affected if The installed version is anything below 25.5.0 (e.g., 25.4.x, 25.3.x, earlier releases)
  3. Verify captive-portal is enabled
    In the ExtremeGuest Essentials admin interface, navigate to the captive-portal or SSID configuration section. Check whether captive-portal authentication is enabled for any wireless networks.
    Affected if Captive-portal authentication is enabled on one or more SSIDs
  4. Review SSID configuration for vulnerable settings
    Examine the SSID configurations where captive-portal is enabled. Look for settings related to authentication retry behavior, client state management, or any configuration that allows repeated login attempts to influence authentication state.
    Affected if The SSID has a configuration that permits repeated login attempts to eventually mark a device as authenticated (specific settings vary by configuration)
  5. Inspect Client360 logs for MAC-username anomaly
    Access the Client360 logging or client authentication logs. Look for entries where the username field displays the client MAC address even though MAC-authentication is not explicitly enabled in your configuration.
    Affected if Client360 logs show client MAC addresses as usernames without MAC-authentication being enabled

Your environment is affected if ExtremeGuest Essentials version is below 25.5.0 AND captive-portal is enabled on SSIDs with certain configurations that allow repeated login attempts to succeed.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 25.5.0 or later
Fixed in 25.5.0
Interim mitigation

Upgrade ExtremeGuest Essentials to version 25.5.0 or later to remediate this vulnerability. Until the upgrade can be applied, consider disabling the affected captive-portal SSIDs or implementing additional network-level access controls to mitigate unauthorized access.

Recommended fix High confidence

25.5.0

  1. Upgrade ExtremeGuest Essentials to version 25.5.0 or later to remediate the vulnerability
  2. After upgrading, verify that the captive-portal properly enforces authentication attempt limits
  3. Review Client360 logs to confirm that unauthorized access attempts are properly logged and blocked

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Extremeguest Essentials Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-8679 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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