Ios XeOperating system · Cisco
CVE-2011-3279
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 provider-edge MPLS NAT implementation in Cisco IOS 12.1 through 12.4 and 15.0 through 15.1, and IOS XE 3.1.xSG, allows remote attackers to cause a denial of service (device reload) via a malformed SIP packet to UDP port 5060, aka Bug ID CSCti98219.
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 confidenceThe vulnerability exists in the provider-edge MPLS NAT implementation of Cisco IOS 12.1-12.4, 15.0-15.1, and IOS XE 3.1.xSG. Remote attackers can cause a denial of service (device reload) by sending malformed SIP (Session Initiation Protocol) packets to UDP port 5060, triggering a crash in the NAT processing path.
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
Ios XeOperating system
= 3.1.0sg= 3.1.1sg
iOSOperating system
>= 12.1, <= 12.4>= 15.0, <= 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
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:L/Au:N/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 IOS/IOS XE versionRun 'show version' on the device CLI to obtain the exact software versionAffected if The version falls within 12.1 through 12.4, 15.0 through 15.1 for IOS, or 3.1.0SG/3.1.1SG for IOS XE
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Verify MPLS NAT is configuredRun 'show ip nat translations' and 'show running-config | include mpls ip nat' to check for NAT configuration in an MPLS environmentAffected if MPLS-based NAT is active on the device
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Confirm SIP processing is enabledRun 'show running-config | include sip' or check if UDP port 5060 is open/listening using 'show udp neighbors' or similar UDP endpoint commandsAffected if SIP traffic or UDP port 5060 is being processed by the device
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Check if device is acting as provider-edgeReview the device role in the network topology and running-config for 'mpls label protocol' and interface configurations in provider-edge facing interfacesAffected if The device functions as a provider-edge router with MPLS enabled
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Assess UDP 5060 exposureCheck interface ACLs and firewall rules to determine if UDP port 5060 traffic from untrusted sources can reach the device NAT processing pathAffected if Unfiltered or unrate-limited SIP packets on UDP 5060 can reach the device from external networks
The device is affected if it runs a vulnerable IOS/IOS XE version, has MPLS NAT enabled, processes SIP traffic, and UDP port 5060 is accessible from potentially malicious external sources.
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 the Cisco IOS security update for bug ID CSCti98219, or implement ACLs at network boundaries to filter or rate-limit SIP traffic on UDP 5060 until patches can be deployed.
Fix this in Ios Xe
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 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 $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-3279 — 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-2011-3279 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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- Version or environment caveats, and links to real fixes
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