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Data MasterOperating system · Asustor

CVE-2026-6643

CRITICAL · 9.9 CVSS v3.1 Published 2026-04-20
Fix available
A fix is available. Upgrade to 4.3.3.RR42 / 5.1.2.reo1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable 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 stack-based buffer overflow vulnerability was found in the VPN Clients on the ADM. The issue stems from the use of unbounded sscanf() and passing user-controlled data directly to printf(). Due to the lack of PIE and Stack Canary protections, an authenticated remote attacker can exploit these to execute arbitrary code as the web server user. Affected products and versions include: from ADM 4.1.0 through ADM 4.3.3.RR42 as well as from ADM 5.0.0 through ADM 5.1.2.REO1.

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

Stack-based buffer overflow in VPN Clients on ADM (Administrative Domain Manager) allows authenticated remote attackers to execute arbitrary code as the web server user. The vulnerability results from unbounded sscanf() calls and direct user-controlled data passed to printf(), compounded by missing PIE (Position Independent Executable) and Stack Canary memory protections.

MitigationUpgrade ADM to a patched version beyond 4.3.3.RR42 or 5.1.2.REO1, or apply vendor-supplied security patches. Until patched, minimize exposure by restricting VPN administration access to trusted users only.

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
Data MasterOperating system
Affected:>= 4.1.0.rhu2, < 4.3.3.RR42>= 5.0.0.ra82, < 5.1.2.reo1

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/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 installed ADM version
    Access ADM settings panel, go to System > System Information, or run 'adm_version' command via SSH to retrieve the exact firmware version string
    Affected if Version begins with 4.1.0.rhu2 or higher through 4.3.3.RR42 (exclusive), or begins with 5.0.0.ra82 or higher through 5.1.2.reo1 (exclusive)
  2. Confirm VPN Client feature is active
    In ADM web interface, navigate to Services > VPN Client, or check /usr/local/AppCentral/vpn-client/ for active processes and configuration files
    Affected if VPN Client service is installed, enabled, or has any configured VPN connections
  3. Check network exposure of VPN services
    Review firewall rules and port forwarding settings for VPN-related ports (OpenVPN typically 1194, PPTP 1723, L2TP 500/4500), or inspect /etc/config/vpn for bound interfaces
    Affected if VPN Client ports are accessible from untrusted networks or the internet without proper access controls
  4. Verify authentication exposure
    Examine /etc/shadow or user management panel to list accounts with VPN Client access permissions, and check if guest or untrusted accounts exist
    Affected if Multiple user accounts have VPN Client permissions, or VPN access is granted to users outside the trusted admin group

You are affected if your ADM version falls within the vulnerable ranges AND the VPN Client feature is enabled with any active configuration or accessible connections.

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 4.3.3.RR42 / 5.1.2.reo1 or later
Fixed in 4.3.3.RR425.1.2.reo1
Interim mitigation

Upgrade ADM to a patched version beyond 4.3.3.RR42 or 5.1.2.REO1, or apply vendor-supplied security patches. Until patched, minimize exposure by restricting VPN administration access to trusted users only.

Recommended fix High confidence

ADM 4.3.3.RR42 (for 4.x branch) or ADM 5.1.2.REO1 (for 5.x branch)

  1. 1. Identify the current ADM version installed on the Asustor device via the ADM dashboard or system information.
  2. 2. Determine which version branch is in use (ADM 4.x or ADM 5.x).
  3. 3. Download the fixed ADM firmware version from Asustor's official support website: www.asustor.com
  4. 4. For ADM 4.x branch: upgrade to version 4.3.3.RR42 or later.
  5. 5. For ADM 5.x branch: upgrade to version 5.1.2.REO1 or later.
  6. 6. Apply the firmware update through the ADM web interface under 'System' > 'ADM Update', or manually upload the firmware file if required.
  7. 7. After reboot, verify the new ADM version is installed and the VPN Client service is functioning normally.
Caveat Standard firmware update risks apply (ensure backups of configuration exist and power stability during update); minor configuration changes may be needed if moving between major version branches

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

Fix this in Data Master Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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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-2026-6643 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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