Cisco 7xx RoutersHardware / appliance · Cisco
CVE-1999-0416
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 · uneditedVulnerability in Cisco 7xx series routers allows a remote attacker to cause a system reload via a TCP connection to the router's TELNET port.
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 vulnerability in Cisco 7xx series routers allows a remote attacker to cause a denial of service (system reload) by sending a TCP connection to the router's TELNET port. The vulnerability appears to stem from improper handling of incoming TELNET connections, causing the router to crash rather than normally processing or rejecting the connection.
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
Cisco 7xx RoutersHardware / appliance
all 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/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 device modelUse 'show version' command or check router hardware label to confirm the device is a Cisco 7xx series router (such as Cisco 701, 702, 712, 716, 720, 730 series)Affected if The device model is any Cisco 7xx series router, as all versions are affected
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Check if TELNET service is enabledUse 'show running-config' or 'show line' command to examine if vty lines have 'transport input telnet' or 'transport input all' configured, or check for 'enable telnet' in the configurationAffected if TELNET is enabled on any vty (lines 0-4) or aux port, allowing incoming connections
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Verify TELNET port accessibilityFrom an external host, attempt to reach the router's management IP on TCP port 23 (for example, using 'telnet <router_ip>' or 'nc -zv <router_ip> 23')Affected if Port 23 responds and accepts connections, indicating the router can receive incoming TELNET traffic
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Check management interface access controlsUse 'show access-lists' and 'show ip interface' to examine if ACLs are applied to vty lines or inbound interfaces that restrict management accessAffected if No ACLs are applied to restrict TELNET access to trusted IP addresses, allowing unauthenticated attackers to trigger the flaw
A defender is affected if they are running a Cisco 7xx series router with TELNET service enabled and port 23 accessible from untrusted networks, as any incoming TELNET connection can trigger the crash.
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 dataDisable TELNET access on affected routers and use SSH for remote management, or upgrade to a supported Cisco router model with current firmware. Implement access control lists to restrict management access to trusted IP addresses.
Fix this in Cisco 7xx Routers
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-1999-0416 — 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-1999-0416 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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