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iOSOperating system · Cisco

CVE-2011-2058

HIGH · 7.5 CVSS v3.1 Published 2011-10-22
Fix available
A fix is available. Upgrade to 12.2 or later.
See remediation →
84/100
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 cat6000-dot1x component in Cisco IOS 12.2 before 12.2(33)SXI7 does not properly handle an external loop between a pair of dot1x enabled ports, which allows remote attackers to cause a denial of service (traffic storm) via unspecified vectors that trigger many unicast EAPoL Protocol Data Units (PDUs), aka Bug ID CSCtq36336.

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 cat6000-dot1x component in Cisco IOS 12.2 before 12.2(33)SXI7 fails to properly handle external loops between a pair of 802.1x-enabled ports. When such a loop exists, unspecified vectors trigger repeated unicast EAPoL (Extensible Authentication Protocol over LAN) Protocol Data Units, creating a traffic storm that causes denial of service.

MitigationUpgrade Cisco IOS to version 12.2(33)SXI7 or later to patch the vulnerability. Additionally, disable 802.1x on unused ports and implement loop prevention controls at the network design level to mitigate similar issues.

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, < 12.2\(33\)sxi7

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
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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. Determine the Cisco IOS version
    Run 'show version' or 'show bootvar' to display the running IOS version
    Affected if The version starts with 12.2 and is earlier than 12.2(33)SXI7 (for example, 12.2(33)SXI6 or earlier)
  2. Check if 802.1x is enabled globally
    Run 'show dot1x' or 'show running-config | include dot1x' to see if 802.1x authentication is enabled on the switch
    Affected if 802.1x is enabled (dot1x system-auth-control is present in the configuration)
  3. Identify 802.1x enabled ports
    Run 'show dot1x interface' or 'show interface switchport' combined with 802.1x status to list ports with dot1x enabled
    Affected if Any ports have 802.1x authentication enabled (Port Control is set to auto or force-authorized)
  4. Inspect network topology for external loops
    Review the physical network topology and cabling between 802.1x-enabled ports, or use 'show spanning-tree' and loop detection tools to identify potential loop paths
    Affected if An external loop cable or network loop exists connecting two 802.1x-enabled ports, creating a path for repeated EAPoL PDUs
  5. Monitor for EAPoL traffic anomalies
    Use 'show interface' statistics or capture traffic on an affected port to observe unusually high rates of EAPoL packets
    Affected if EAPoL packet counts are abnormally high or increasing rapidly without corresponding legitimate authentication activity

The environment is affected if the switch runs a vulnerable IOS version (12.2 before 12.2(33)SXI7), 802.1x is enabled on ports, and an external loop exists between two 802.1x-enabled ports that can trigger the traffic storm.

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
Upgrade available Upgrade to 12.2 or later
Fixed in 12.2
Interim mitigation

Upgrade Cisco IOS to version 12.2(33)SXI7 or later to patch the vulnerability. Additionally, disable 802.1x on unused ports and implement loop prevention controls at the network design level to mitigate similar issues.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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-2011-2058 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