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Ios XeOperating system · Cisco

CVE-2013-6979

MEDIUM · 5.4 CVSS v2.0 Published 2013-12-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
63/100
Remediation priority · Elevated
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 VTY authentication implementation in Cisco IOS XE 03.02.xxSE and 03.03.xxSE incorrectly relies on the Linux-IOS internal-network configuration, which allows remote attackers to bypass authentication by leveraging access to a 192.168.x.2 source IP address, aka Bug ID CSCuj90227.

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 confidence

The VTY (Virtual Teletype) authentication in Cisco IOS XE 03.02.xxSE and 03.03.xxSE incorrectly trusts internal-network traffic from 192.168.x.2 IP addresses due to improper handling of the Linux-IOS internal-network configuration. This allows remote attackers who can source traffic from a 192.168.x.2 address to bypass VTY authentication entirely and gain unauthorized administrative access to the device.

MitigationApply the appropriate Cisco IOS XE security update or upgrade to a patched version beyond 03.03.xxSE. If immediate patching is not feasible, implement additional authentication controls (such as AAA with TACACS+/RADIUS) and restrict VTY access to trusted management networks rather than relying on source IP validation.

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
Ios XeOperating system
Affected:all versions

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
High
Authentication
None
Confidentiality
Complete
Integrity
None
Availability
None

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

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 XE version
    Run 'show version' or 'show version | include Version' to retrieve the installed IOS XE version string
    Affected if The version is 03.02.xxSE or 03.03.xxSE (any xx placeholder indicates the affected range)
  2. Examine VTY line configuration
    Run 'show running-config | begin line vty' to view VTY line configurations and check for 'ip verify unicast source' or 'transport input ssh' settings
    Affected if VTY lines are configured without proper source IP verification or rely on trusted internal network source addresses
  3. Check for 192.168.x.2 addresses in configuration
    Run 'show running-config | include 192.168' to search for any 192.168.x.2 IP addresses assigned to interfaces or used in access-lists
    Affected if The configuration contains 192.168.x.2 addresses that could be spoofed by an attacker to bypass authentication
  4. Review VTY access-class bindings
    Run 'show line vty' and 'show running-config | include access-class' to see if VTY lines have access-class restrictions applied
    Affected if VTY lines lack access-class controls or rely solely on source IP-based trust without additional AAA authentication

A system is affected if it runs Cisco IOS XE 03.02.xxSE or 03.03.xxSE with VTY lines configured to trust traffic from 192.168.x.2 addresses without enforcing strong authentication.

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

Apply the appropriate Cisco IOS XE security update or upgrade to a patched version beyond 03.03.xxSE. If immediate patching is not feasible, implement additional authentication controls (such as AAA with TACACS+/RADIUS) and restrict VTY access to trusted management networks rather than relying on source IP validation.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2013-6979 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
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  • Version or environment caveats, and links to real fixes
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