Nx OsOperating system · Cisco
CVE-2012-4098
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 BGP implementation in Cisco NX-OS does not properly filter AS paths, which allows remote attackers to cause a denial of service (BGP service reset and resync) via a malformed UPDATE message, aka Bug ID CSCtn13055.
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 BGP implementation in Cisco NX-OS fails to properly validate/filter AS (Autonomous System) path attributes in BGP UPDATE messages. This allows remote attackers to send malformed UPDATE messages that trigger a BGP service reset and resync, causing denial of service.
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
Nx OsOperating system
all versionsCVSS 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
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 NX-OS device to confirm it is running Cisco NX-OS and note the installed version numberAffected if The device runs any version of Cisco NX-OS (all versions are affected)
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Confirm BGP is enabledRun 'show bgp summary' or 'show ip bgp' to verify BGP is configured and activeAffected if BGP is enabled and the device is processing BGP UPDATE messages
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Check BGP configuration for AS path filteringRun 'show running-config bgp' and inspect for route-maps, as-path access-lists, or prefix-lists that filter AS path attributesAffected if No AS path filtering is configured in BGP (the device accepts UPDATE messages without AS path validation)
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Inspect BGP neighbor policiesRun 'show bgp neighbors' and review the 'Policy' field for each neighbor to see if inbound route policies include AS path filteringAffected if BGP neighbors do not have inbound AS path filtering policies applied
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Review BGP route maps for AS path match statementsExamine configured route-maps using 'show route-map' and look for 'match as-path' statements that validate AS path attributesAffected if No route-maps with AS path matching are defined or applied to BGP peers
The environment is affected if the device runs Cisco NX-OS with BGP enabled and without AS path filtering configured on BGP peers to reject malformed UPDATE messages
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 NX-OS software update that addresses this vulnerability, or implement BGP AS path filtering/validation on BGP peers to reject malformed UPDATE messages as an interim workaround.
Fix this in Nx Os
Scoped from the published advisory
- Consultation6.0 h
- Implementation12.0 h
- Testing10.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-4098 — 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-2012-4098 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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