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iOSOperating system · Cisco

CVE-2011-1640

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 ethernet-lldp component in Cisco IOS 12.2 before 12.2(33)SXJ1 does not properly support a large number of LLDP Management Address (MA) TLVs, which allows remote attackers to cause a denial of service (device crash) via crafted LLDPDUs, aka Bug ID CSCtj22354.

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

A vulnerability in the ethernet-lldp component of Cisco IOS 12.2 allows remote attackers to crash the device by sending crafted LLDPDUs containing a large number of LLDP Management Address (MA) TLVs. The device fails to properly process these TLVs, resulting in a denial of service.

MitigationUpgrade Cisco IOS to version 12.2(33)SXJ1 or later to obtain the patch. Additionally, disable LLDP on untrusted network segments or implement port-level access controls to limit which devices can send LLDPDUs.

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\(33\)sxj1

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 Cisco IOS version
    Execute 'show version' on the device console or via remote access. Locate the version string in the output (typically displayed as 'Cisco IOS Software, Version 12.2(...)' or similar).
    Affected if The displayed version is 12.2 or any 12.2(x) release, and is lower than 12.2(33)sxj1.
  2. Confirm LLDP is enabled
    Execute 'show lldp' or 'show lldp neighbors' to check if LLDP is running. Alternatively, use 'show running-config | include lldp' to verify LLDP configuration in the active config.
    Affected if LLDP is actively running on one or more interfaces (the vulnerability only affects devices where the ethernet-lldp component is processing traffic).

You are affected if your device runs any Cisco IOS version from 12.2 up to but not including 12.2(33)sxj1, and LLDP is enabled on the device.

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)SXJ1 or later to obtain the patch. Additionally, disable LLDP on untrusted network segments or implement port-level access controls to limit which devices can send LLDPDUs.

Fix this in iOS Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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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-2011-1640 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