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Ios XeOperating system · Cisco

CVE-2011-3276

HIGH · 7.8 CVSS v2.0 Published 2011-10-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
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
Unspecified vulnerability in the 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 or hang) by sending crafted SIP packets to TCP port 5060, aka Bug ID CSCso02147.

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

Vulnerability in Cisco IOS NAT implementation allows remote attackers to cause denial of service by sending crafted SIP (Session Initiation Protocol) packets to TCP port 5060, causing affected devices to reload or hang. The flaw exists in IOS versions 12.1-12.4 and 15.0-15.1, and IOS XE 3.1.xSG.

MitigationApply Cisco IOS updates from Bug ID CSCso02147; as interim measures, filter or block untrusted SIP traffic at network perimeter and restrict access to TCP port 5060 using ACLs.

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
Affected:= 3.1.0sg= 3.1.1sg
iOSOperating system
Affected:= 12.1= 12.1e= 12.2= 12.2b= 12.2bc= 12.2bx= 12.2cx= 12.2cz= 12.2ew= 12.2ewa= 12.2ex= 12.2ey

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Cisco platform and OS type
    Determine whether the device runs Cisco IOS or Cisco IOS XE using 'show version' or similar system information command
    Affected if Device runs Cisco IOS or IOS XE
  2. Check the installed IOS version
    Use 'show version' to retrieve the running IOS version number and compare it against the affected ranges: 12.1 through 12.4, 15.0 through 15.1 for iOS, or 3.1.0sg through 3.1.1sg for IOS XE
    Affected if Installed version falls within the affected ranges
  3. Verify NAT is configured on the device
    Use 'show ip nat statistics' or 'show running-config | include ip nat' to check if Network Address Translation is enabled
    Affected if NAT is configured and running
  4. Confirm SIP traffic handling is enabled
    Check if the device is configured to handle SIP traffic on TCP port 5060 using 'show running-config | include sip' or by reviewing ACLs and inspection rules for port 5060
    Affected if Device processes or inspects SIP traffic on TCP port 5060
  5. Assess exposure to untrusted SIP traffic
    Review inbound ACLs on external interfaces to determine if TCP port 5060 traffic from untrusted sources is permitted
    Affected if TCP port 5060 is accessible from untrusted networks

The device is affected if it runs a vulnerable iOS or IOS XE version, has NAT enabled, processes SIP traffic on TCP port 5060, and allows that traffic from untrusted sources.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco IOS updates from Bug ID CSCso02147; as interim measures, filter or block untrusted SIP traffic at network perimeter and restrict access to TCP port 5060 using ACLs.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2011-3276 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
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