iOSOperating system · Cisco
CVE-2011-4231
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 · uneditedCisco IOS 15.1 and 15.2 and IOS XE 3.x, when configured as an IPsec hub with X.509 certificates in use, allows remote authenticated users to cause a denial of service (segmentation fault and device crash) via unspecified vectors, aka Bug ID CSCtq61128.
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 confidenceDenial of service vulnerability in Cisco IOS 15.1/15.2 and IOS XE 3.x when configured as an IPsec hub using X.509 certificates. Authenticated remote users can send unspecified vectors causing a segmentation fault and device reload.
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
= 15.1= 15.2
Ios XeOperating system
= 3.1.0s= 3.1.0sg= 3.1.1s= 3.1.1sg= 3.1.2s= 3.1.3s= 3.1.4s= 3.2.0s= 3.2.0sg= 3.2.1s= 3.2.2s= 3.3.0sCVSS 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
- M
- Authentication
- Single
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:M/Au:S/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 checksWork through these to decide whether this CVE applies to you.
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Identify the Cisco IOS or IOS XE versionRun 'show version' on the device CLI and note the software version numberAffected if The version begins with 15.1, 15.2, or is in the IOS XE 3.1.x through 3.3.x range
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Verify if IPsec is configuredRun 'show crypto ipsec sa' or 'show crypto isakmp sa' to check for active IPsec security associationsAffected if IPsec tunnels or security associations are present on the device
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Confirm the device is configured as an IPsec hubReview the running configuration with 'show running-config' and look for 'crypto isakmp profile' or 'crypto ipsec profile' statements that designate hub-mode behavior, or check for multiple spoke peer definitionsAffected if The device is configured to terminate IPsec connections from multiple remote peers (hub role)
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Check if X.509 certificate authentication is enabled for IPsecRun 'show crypto pki certificates' and inspect the ISAKMP profile configuration via 'show running-config | include isakmp' for 'authentication user-certificate' or 'certificate' statementsAffected if X.509 certificate-based authentication is configured (as opposed to pre-shared key authentication)
The device is affected if it runs IOS 15.1/15.2 or IOS XE 3.x, is configured as an IPsec hub, and uses X.509 certificates for IPsec authentication.
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 dataApply Cisco software updates addressing Bug ID CSCtq61128; as a potential workaround, evaluate whether X.509 certificate-based authentication can be disabled or alternative authentication methods used until the patch is deployed.
Fix this in iOS
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-4231 — 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-2011-4231 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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