CVE-2001-1135
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 · uneditedZyXEL Prestige 642R and 642R-I routers do not filter the routers' Telnet and FTP ports on the external WAN interface from inside access, allowing someone on an internal computer to reconfigure the router, if the password is known.
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 Prestige 642R and 642R-I routers lack proper firewall filtering on the WAN interface, allowing internal hosts to access the router's Telnet (port 23) and FTP (port 21) services that should be blocked from external exposure. This enables an attacker with internal network access and the router password to reconfigure the device.
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= 642rCVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
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 router modelAccess the router's web interface or console and check the device model information under System Status or similar sectionAffected if The device is not a ZyXEL Prestige 642R or 642R-I model
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Verify Telnet service statusAttempt to connect to the router's WAN IP address on TCP port 23 from an external network or use the router's admin interface to check if Telnet service is enabledAffected if Telnet service is enabled and accessible from the WAN interface on port 23
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Verify FTP service statusAttempt to connect to the router's WAN IP address on TCP port 21 from an external network or use the router's admin interface to check if FTP service is enabledAffected if FTP service is enabled and accessible from the WAN interface on port 21
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Inspect WAN firewall rulesAccess the router's firewall configuration section and review the inbound filter rules applied to the WAN interface to see if Telnet (port 23) and FTP (port 21) are explicitly blocked or filteredAffected if No firewall rule exists to block or filter Telnet and FTP traffic arriving on the WAN interface
The device is affected if it is a ZyXEL Prestige 642R/642R-I with Telnet or FTP services enabled and accessible from the WAN interface without proper firewall filtering rules in place.
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.
From vendor dataConfigure the router's firewall rules to explicitly block or filter Telnet and FTP access from the WAN interface, or disable these services entirely if not required for remote management.
- 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-2001-1135 — 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-2001-1135 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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