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iOSOperating system · Cisco

CVE-2013-5474

HIGH · 7.8 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 →
87/100
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
Race condition in the IPv6 virtual fragmentation reassembly (VFR) implementation in Cisco IOS 12.2 through 12.4 and 15.0 through 15.3 allows remote attackers to cause a denial of service (device reload or hang) via fragmented IPv6 packets, aka Bug ID CSCud64812.

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

A race condition exists in the IPv6 Virtual Fragmentation Reassembly (VFR) feature of Cisco IOS versions 12.2 through 12.4 and 15.0 through 15.3. Remote attackers can exploit this by sending specially crafted fragmented IPv6 packets to trigger the race condition, causing the affected device to reload or hang, resulting in denial of service.

MitigationApply the appropriate Cisco IOS patch for Bug ID CSCud64812, or upgrade to a Cisco IOS version beyond 15.3 that is not affected. If VFR is not required in the environment, it can be disabled to eliminate the attack surface.

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= 12.3= 12.4= 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
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:L/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 Cisco IOS version
    Execute 'show version' and locate the IOS release line (e.g., 'Version 15.2(4)E')
    Affected if The version number falls within 12.2.x through 12.4.x, or 15.0.x through 15.3.x
  2. Verify IPv6 is enabled
    Run 'show ipv6 general-prefix' or check running configuration for 'ipv6 unicast-routing'
    Affected if IPv6 routing or features are actively enabled on the device
  3. Confirm VFR is configured
    Run 'show running-config | include virtual-reassembly' or check for 'ipv6 virtual-reassembly' in the configuration
    Affected if The VFR feature (ipv6 virtual-reassembly) is enabled in the active configuration
  4. Check VFR process status
    Execute 'show ipv6 virtual-reassembly' to display VFR interface settings and statistics
    Affected if VFR is actively processing fragments on any interface

The device is affected if it runs a Cisco IOS version in the 12.2-12.4 or 15.0-15.3 range, has IPv6 enabled, and has VFR (ipv6 virtual-reassembly) configured or active.

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 patch for Bug ID CSCud64812, or upgrade to a Cisco IOS version beyond 15.3 that is not affected. If VFR is not required in the environment, it can be disabled to eliminate the attack surface.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
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Scan for this in your stack

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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-2013-5474 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
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