CVE-2025-0890
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** Insecure default credentials for the Telnet function in the legacy DSL CPE Zyxel VMG4325-B10A firmware version 1.00(AAFR.4)C0_20170615 could allow an attacker to log in to the management interface if the administrators have the option to change the default credentials but fail to do so.
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 confidenceThe Zyxel VMG4325-B10A DSL router firmware contains hardcoded default credentials for its Telnet management service. An attacker with network access to the device can authenticate using these default credentials to gain full administrative access to the router's 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 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
- 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 checksWork through these to decide whether this CVE applies to you.
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Identify device modelAccess the router web interface or check the device label to determine the exact model number (e.g., VMG4325-B10A, SBG3500-N000, VMG1312-B10A/B10B/B10E, VMG3312-B10A, VMG3313-B10A, VMG3926-B10B)Affected if The device model matches any of the listed affected models
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Verify Telnet service statusLog into the router web interface and navigate to Management > Access Control > Services or similar section to check if Telnet management service is enabledAffected if Telnet service is enabled and accessible on the device
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Check network exposure of Telnet portFrom a remote network location, attempt to connect to the device's IP on TCP port 23 (e.g., using telnet client or port scanner) to verify if Telnet port is reachableAffected if Telnet port 23 is accessible from the network (not blocked by firewall or VLAN isolation)
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Confirm default credentials are changedAttempt to log in via Telnet using the device's default administrative username and password (consult device documentation for manufacturer defaults), or check if credentials have been modified from factory defaultsAffected if The default credentials have not been changed and still allow authentication
If the device is one of the affected Zyxel models, Telnet is enabled, and the default credentials remain unchanged or Telnet is network-accessible, the environment is affected by CVE-2025-0890
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 this is an end-of-life legacy device (UNSUPPORTED), the recommended remediation is to replace it with a currently supported model. If continued use is required, immediately change the default credentials, disable Telnet if unused, and isolate the device on a restricted network segment.
- 1. Disable the Telnet service on the device if it is not required for business operations
- 2. If Telnet is required, immediately change the default credentials to a strong, unique password
- 3. Configure firewall rules to restrict access to the Telnet port (port 23) to only authorized IP addresses or management networks
- 4. Implement network segmentation to isolate the affected devices from sensitive network segments
- 5. If the device is no longer actively maintained by the vendor, consider replacing it with a supported model that receives security updates
- 6. Audit all devices for default credentials and enforce password policies
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-0890 — 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-2025-0890 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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