CVE-2024-40891
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**UNSUPPORTED WHEN ASSIGNED** A post-authentication command injection vulnerability in the management commands of the legacy DSL CPE Zyxel VMG4325-B10A firmware version 1.00(AAFR.4)C0_20170615 could allow an authenticated attacker to execute operating system (OS) commands on an affected device via Telnet.
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 confidenceA post-authentication command injection vulnerability exists in the Telnet management interface of Zyxel VMG4325-B10A firmware version 1.00(AAFR.4)C0_20170615. An authenticated attacker can inject and execute arbitrary operating system commands through management commands sent via Telnet, leading to full device compromise.
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 dataall versionsall versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 checksWork through these to decide whether this CVE applies to you.
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Identify the device modelAccess the router web interface or check the device label to confirm the exact model number (e.g., VMG4325-B10A, VMG1312-B10A, etc.)Affected if The model matches one of the affected models: Vmg1312 B10a/b/e, Vmg3312 B10a, Vmg3313 B10a, Vmg3926 B10b, Vmg4325 B10a, Vmg4380 B10a
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Verify Telnet service statusLog into the router web interface and navigate to Network Settings > Remote Management or similar, or use a network scanner to check if port 23 is open and responding on the device IPAffected if Telnet service is enabled and accessible on the device
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Confirm management access scopeCheck the router configuration for allowed IP addresses or subnets for Telnet/remote management access. Verify if management interface is reachable from WAN or untrusted networksAffected if Telnet management is exposed to untrusted networks or unauthorized IP addresses
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Review for unauthorized access indicatorsExamine router logs or network traffic logs for Telnet connection attempts, especially from unexpected source IPs or containing unusual command patternsAffected if There are Telnet connections or commands in logs that were not initiated by authorized administrators
A defender is affected if they operate any of the listed Zyxel VMG router models with Telnet management interface enabled, particularly if accessible from untrusted networks.
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 · scopedSince the device is marked unsupported, prioritize upgrading to a supported firmware version if available. If no update exists, disable Telnet access, enforce strong authentication, and consider replacing the end-of-life device with a currently supported model.
- 1. Identify all affected Zyxel devices (Vmg1312, Vmg3312, Vmg3313, Vmg3926, Vmg4325, Vmg4380 series) on the network.
- 2. Disable Telnet access on affected devices if enabled, as the vulnerability is exploited via Telnet.
- 3. If Telnet cannot be disabled, implement network segmentation to restrict access to the management interface to trusted networks only.
- 4. Ensure strong authentication is in place for any remaining management access.
- 5. Monitor for any suspicious activity or unauthorized access attempts.
- 6. Plan for eventual replacement of these legacy devices with currently supported hardware.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
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Free · runs locallyCheck whether your project pulls in CVE-2024-40891 — 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-2024-40891 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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- Version or environment caveats, and links to real fixes
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