iOSOperating system · Cisco
CVE-2011-3271
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 · uneditedUnspecified vulnerability in the Smart Install functionality in Cisco IOS 12.2 and 15.1 allows remote attackers to execute arbitrary code or cause a denial of service (device crash) via crafted TCP packets to port 4786, aka Bug ID CSCto10165.
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 confidenceCritical vulnerability in Cisco IOS Smart Install functionality allows remote attackers to execute arbitrary code or cause device crash via crafted TCP packets to port 4786. This is a pre-authentication remote code execution flaw affecting IOS 12.2 and 15.1, enabling complete compromise of affected network infrastructure devices.
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
= 12.2= 15.1CVSS 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
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:N/AC:L/Au:N/C:C/I:C/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 checksWork through these to decide whether this CVE applies to you.
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Identify Cisco IOS versionRun 'show version' command on the device to retrieve the installed IOS version number. Look for version strings starting with 12.2 or 15.1.Affected if The device runs Cisco IOS version 12.2 or 15.1 family releases.
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Verify Smart Install feature statusRun 'show vstack config' or 'show vstack status' command to check if Smart Install (also known as VStack) feature is configured on the device.Affected if Smart Install feature is enabled or configured on the device.
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Check TCP port 4786 listenerRun 'show control-plane host open-port' or 'show listeners tcp' command (if available) to determine if the device is listening on TCP port 4786.Affected if The device has TCP port 4786 open and listening for Smart Install traffic.
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Assess network exposure of port 4786Review access control lists and interface configurations to determine if TCP port 4786 is reachable from untrusted network segments. Use 'show access-lists' and 'show ip interface' commands.Affected if TCP port 4786 is accessible from untrusted or external network paths without ACL restrictions.
A device is affected if it runs Cisco IOS 12.2 or 15.1, has Smart Install feature enabled, and has TCP port 4786 exposed to untrusted traffic.
Generated from the published advisory. Verify against your own configuration.
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.
dbcve · scopedDisable Smart Install functionality on affected Cisco IOS devices if not required, or implement strict ACLs to block untrusted access to TCP port 4786. Apply Cisco IOS security updates to address Bug ID CSCto10165.
Cisco IOS 15.2(4) or later, or a later 12.2 release that includes the security fix
- Disable the Smart Install feature using the 'no vstack' command in global configuration mode
- Alternatively, block TCP port 4786 at network boundaries to prevent external exploitation
- Upgrade Cisco IOS to a version that includes the fix for CSCto10165
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in iOS
Scoped from the published advisory
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,680.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-3271 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2011-3271 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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