dbcve.org
Fgw3000 Ah FirmwareOperating system · Linksys

CVE-2025-4999

CRITICAL · 9.8 CVSS v3.1 Published 2025-05-20
Fix available
A fix is available. Upgrade to after 1.0.17.000000 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
A vulnerability was found in Linksys FGW3000-AH and FGW3000-HK up to 1.0.17.000000 and classified as critical. Affected by this issue is the function sub_4153FC of the file /cgi-bin/sysconf.cgi of the component HTTP POST Request Handler. The manipulation of the argument supplicant_rnd_id_en leads to command injection. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

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 confidence

Command injection vulnerability in Linksys FGW3000-AH and FGW3000-HK routers (up to firmware 1.0.17.000000). The supplicant_rnd_id_en parameter in /cgi-bin/sysconf.cgi is not sanitized before being passed to a system call, allowing remote attackers to execute arbitrary OS commands. Public exploit availability and CVSS 9.8 indicate critical risk with trivial exploitability.

MitigationSince no vendor patch is available, restrict network exposure by disabling remote web management, placing the device behind a firewall, or replacing the affected hardware. If the device must remain in production, implement strict network access controls to prevent unauthorized access to the management interface.

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
Fgw3000 Ah FirmwareOperating system
Affected:<= 1.0.17.000000
Fgw3000 Hk FirmwareOperating system
Affected:<= 1.0.17.000000

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. Identify device model
    Access the router admin interface or check the device label to confirm the model is Linksys FGW3000-AH or FGW3000-HK
    Affected if Model is FGW3000-AH or FGW3000-HK
  2. Check firmware version
    Navigate to the router web interface (typically Status or System Info page) or use the command line to retrieve the firmware version. Common paths: admin panel firmware upgrade page or via SNMP/Telnet if available
    Affected if Firmware version is 1.0.17.000000 or lower
  3. Confirm remote web management is accessible
    Attempt to access the router web interface from an external network IP address (the CGI endpoint /cgi-bin/sysconf.cgi). Check if port 80 or 443 is open to external IPs
    Affected if The management web interface (port 80/443) is reachable from untrusted networks
  4. Verify the vulnerable CGI endpoint exists
    Send a request to http://<router-ip>/cgi-bin/sysconf.cgi and observe if the endpoint responds. The vulnerability exists in the supplicant_rnd_id_en parameter
    Affected if The /cgi-bin/sysconf.cgi endpoint is accessible and processes the supplicant_rnd_id_en parameter without sanitization

The device is affected if it is a Linksys FGW3000-AH or FGW3000-HK router running firmware version 1.0.17.000000 or lower, and the web management interface is accessible to the attacker.

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 a release after 1.0.17.000000
Interim mitigation

Since no vendor patch is available, restrict network exposure by disabling remote web management, placing the device behind a firewall, or replacing the affected hardware. If the device must remain in production, implement strict network access controls to prevent unauthorized access to the management interface.

Recommended fix Moderate confidence

Any Linksys FGW3000-AH or FGW3000-HK firmware version newer than 1.0.17.000000 (e.g., 1.0.18.x or later)

  1. 1. Identify the exact model number (FGW3000-AH or FGW3000-HK) of the affected Linksys device
  2. 2. Access the device administration interface and navigate to the firmware/version information section to confirm the current firmware version
  3. 3. Visit the official Linksys support website at www.linksys.com and locate the firmware download section for the FGW3000 series
  4. 4. Download the latest available firmware version for your specific model (note: versions newer than 1.0.17.000000 should contain the fix)
  5. 5. Upload and apply the new firmware through the device's web interface or administrative console
  6. 6. After reboot, verify the new firmware version is installed and confirm the vulnerability is remediated
  7. 7. If no newer firmware is available from Linksys, contact Linksys technical support directly to request the security update
Caveat Firmware upgrades carry inherent risk of device failure if interrupted; ensure stable power during upgrade; backup configuration if possible; upgrade may reset device to factory defaults

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

Fix this in Fgw3000 Ah Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2025-4999 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