iOSOperating system · Cisco
CVE-2011-4667
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 · uneditedThe encryption library in Cisco IOS Software 15.2(1)T, 15.2(1)T1, and 15.2(2)T, Cisco NX-OS in Cisco MDS 9222i Multiservice Modular Switch, Cisco MDS 9000 18/4-Port Multiservice Module, and Cisco MDS 9000 Storage Services Node module before 5.2(6), and Cisco IOS in Cisco VPN Services Port Adaptor for Catalyst 6500 12.2(33)SXI, and 12.2(33)SXJ when IP Security (aka IPSec) is used, allows remote attackers to obtain unencrypted packets from encrypted sessions.
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 confidenceThe encryption library in Cisco IOS and NX-OS has a flaw that allows remote attackers to obtain unencrypted packets from IPSec-encrypted sessions. This represents a fundamental bypass of encryption confidentiality protections, exposing sensitive data that should be protected by IPSec VPNs.
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\(33\)sxi= 12.2\(33\)sxj= 15.2\(1\)t= 15.2\(1\)t1= 15.2\(2\)t
Nx OsOperating system
= 5.0\(5\)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
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify device OS and versionRun 'show version' on the Cisco device CLI to display the installed IOS or NX-OS versionAffected if The displayed version matches 12.2(33)sxi, 12.2(33)sxj, 15.2(1)t, 15.2(1)t1, 15.2(2)t for IOS, or 5.0(5) for NX-OS
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Verify IPSec configurationRun 'show crypto ipsec sa' to check for active IPSec security associationsAffected if IPSec tunnels are active and the device runs an affected version
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Check encryption library in useRun 'show crypto engine configuration' to confirm the device uses the built-in IOS/NX-OS encryption library for IPSecAffected if The device uses the native Cisco encryption library for IPSec and runs an affected version
A device is affected if it runs Cisco IOS version 12.2(33)sxi, 12.2(33)sxj, 15.2(1)t, 15.2(1)t1, or 15.2(2)t, or NX-OS version 5.0(5), and has IPSec tunnels configured using the native encryption library.
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.
From vendor dataUpgrade affected Cisco IOS and NX-OS versions to patched releases beyond 15.2(1)T, 15.2(1)T1, 15.2(2)T, and MDS versions before 5.2(6). Verify IPSec session integrity post-upgrade.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-4667 — 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-2011-4667 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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