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Nx OsOperating system · Cisco

CVE-2015-4323

MEDIUM · 6.1 CVSS v2.0 Published 2015-08-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
66/100
Remediation priority · Elevated
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
Buffer overflow in Cisco NX-OS on Nexus 1000V devices for VMware vSphere 7.3(0)ZN(0.9); Nexus 3000 devices 6.0(2)U5(1.41), 7.0(3)I2(0.373), and 7.3(0)ZN(0.83); Nexus 4000 devices 4.1(2)E1(1b); Nexus 7000 devices 6.2(14)S1; Nexus 9000 devices 7.3(0)ZN(0.9); and MDS 9000 devices 6.2 (13) and 7.1(0)ZN(91.99) and MDS SAN-OS 7.1(0)ZN(91.99) allows remote attackers to cause a denial of service (device outage) via a crafted ARP packet, related to incorrect MTU validation, aka Bug IDs CSCuv71933, CSCuv61341, CSCuv61321, CSCuu78074, CSCut37060, CSCuv61266, CSCuv61351, CSCuv61358, and CSCuv61366.

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

A buffer overflow vulnerability exists in Cisco NX-OS across multiple product lines (Nexus 1000V, 3000, 4000, 7000, 9000, and MDS 9000 series). The flaw stems from incorrect MTU validation when processing ARP packets. Remote attackers can exploit this by sending specially crafted ARP packets with manipulated sizes, causing a buffer overflow that leads to device outage and denial of service.

MitigationApply the relevant Cisco firmware updates corresponding to theBug IDs (CSCuv71933, CSCuv61341, etc.) for the affected device versions. If patches are unavailable, implement network-level filtering to block malformed ARP packets reaching affected devices.

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
Affected:= 6.2\(14\)s1= 6.0\(2\)u5\(1.41\)= 7.0\(3\)i2\(0.373\)= 7.3\(0\)zn\(0.83\)= 7.3\(0\)zn\(0.9\)= 4.1\(2\)e1\(1b\)
Mds 9000 Nx OsOperating system
Affected:= 6.2\(13\)= 7.1\(0\)zn\(91.99\)

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
Adjacent
Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:A/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 device model
    Run 'show version' or 'show inventory' to confirm the device is a Nexus 1000V, 3000, 4000, 7000, 9000, or MDS 9000 series switch
    Affected if Device is NOT one of these Nexus or MDS series products (the vulnerability only affects these product lines)
  2. Check the NX-OS version
    Run 'show version' and locate the 'NX-OS' or 'system:' version line. Compare your installed version against the affected versions: 6.2(14)s1, 6.0(2)u5(1.41), 7.0(3)i2(0.373), 7.3(0)zn(0.83), 7.3(0)zn(0.9), 4.1(2)e1(1b) for NX-OS; 6.2(13), 7.1(0)zn(91.99) for MDS 9000
    Affected if The running NX-OS version matches one of these specific versions exactly
  3. Verify ARP processing is enabled
    Run 'show ip arp' or 'show interface' to confirm ARP is active on at least one interface. This is typically enabled by default on layer 3 interfaces
    Affected if ARP is disabled on all interfaces (unlikely as this is default-enabled)
  4. Check for inbound ARP packet filtering
    Run 'show access-lists' and 'show ip access-lists' to inspect any ACLs applied to ingress interfaces. Verify if there are explicit deny rules or ACLs filtering ARP traffic
    Affected if No ACLs or filters are configured to block malformed or oversized ARP packets at the network edge

The environment is affected if the device is a Cisco Nexus or MDS 9000 series running one of the specific NX-OS versions listed and ARP processing is enabled with no inbound ARP filtering in place.

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 the relevant Cisco firmware updates corresponding to theBug IDs (CSCuv71933, CSCuv61341, etc.) for the affected device versions. If patches are unavailable, implement network-level filtering to block malformed ARP packets reaching affected devices.

Fix this in Nx Os Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2015-4323 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data