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iOSOperating system · Cisco

CVE-2013-5481

HIGH · 7.1 CVSS v2.0 Published 2013-09-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Remotely reachable No privileges 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
The PPTP implementation in Cisco IOS 12.2 and 15.0 through 15.3, when NAT is used, allows remote attackers to cause a denial of service (device reload) via crafted TCP port-1723 packets, aka Bug ID CSCtq14817.

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 confidence

The PPTP implementation in Cisco IOS 12.2 and 15.0 through 15.3 contains a vulnerability when NAT is in use, where specially crafted TCP packets sent to port 1723 can trigger a device reload, causing denial of service.

MitigationUpgrade to a patched Cisco IOS version, or disable PPTP and filter TCP port 1723 traffic on NAT-enabled interfaces if the protocol is not required.

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
iOSOperating system
Affected:= 12.2= 15.0= 15.1= 15.2= 15.3

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
M
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:M/Au:N/C:N/I:N/A:C

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 the Cisco IOS version
    Run 'show version' and locate the IOS release string (e.g., 12.2(XX), 15.X(X)) in the output
    Affected if The version begins with 12.2, 15.0, 15.1, 15.2, or 15.3
  2. Confirm PPTP is enabled
    Run 'show running-config | include pptp' or 'show running-config | include 1723' to search for PPTP-related configuration
    Affected if PPTP configuration (such as 'vpdn' or 'interface Virtual-Template') or any reference to port 1723 appears in the configuration
  3. Verify NAT is active on the device
    Run 'show ip nat translations' or 'show running-config | include ip nat' to check for NAT configuration
    Affected if NAT is configured and actively translating traffic (ip nat inside/outside statements present)
  4. Confirm PPTP traffic can reach the NAT edge
    Review access-lists or firewall policies on the NAT interface to determine if inbound TCP port 1723 traffic is permitted
    Affected if TCP port 1723 traffic from external networks is allowed through the NAT-enabled interface without filtering

You are affected if your device runs Cisco IOS 12.2, 15.0, 15.1, 15.2, or 15.3, has PPTP enabled, and NAT is in use with TCP port 1723 exposed to untrusted networks.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to a patched Cisco IOS version, or disable PPTP and filter TCP port 1723 traffic on NAT-enabled interfaces if the protocol is not required.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2013-5481 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data