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NULL Pointer DereferenceWeakness · CWE-476

CVE-2024-20446

HIGH · 8.6 CVSS v3.1 Published 2024-08-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
Remediation priority · Urgent
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
A vulnerability in the DHCPv6 relay agent of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of specific fields in a DHCPv6 RELAY-REPLY message. An attacker could exploit this vulnerability by sending a crafted DHCPv6 packet to any IPv6 address that is configured on an affected device. A successful exploit could allow the attacker to cause the dhcp_snoop process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition.

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 vulnerability in the DHCPv6 relay agent of Cisco NX-OS Software allows an unauthenticated, remote attacker to cause denial of service by sending a crafted DHCPv6 RELAY-REPLY message to any IPv6 address on the affected device. The improper handling of specific fields in the RELAY-REPLY packet causes the dhcp_snoop process to crash and restart repeatedly, triggering a device reload.

MitigationApply the Cisco-provided software update/patch for NX-OS to address this vulnerability. If immediate patching is not possible, consider disabling DHCPv6 relay functionality or restricting IPv6 access to trusted sources via ACLs as a temporary workaround.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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. Verify DHCPv6 relay feature is enabled
    Execute 'show feature | include dhcpv6' or 'show running-config | include dhcpv6_relay' in NX-OS CLI. The feature must be enabled for the vulnerability to be exploitable.
    Affected if DHCPv6 relay feature (dhcpv6_relay) is enabled on the device
  2. Determine NX-OS software version
    Execute 'show version' or 'show version | include NXOS' to retrieve the running NX-OS version string.
    Affected if The installed NX-OS version falls within the affected version range for this CVE (compare against Cisco's official advisory for your specific platform)
  3. Check for dhcp_snoop process instability
    Execute 'show process cpu history' or 'show system internal sysmgr service name dhcp_snoop' to examine dhcp_snoop process crash history. Also check 'show logging' for dhcp_snoop crash messages.
    Affected if Multiple dhcp_snoop process crashes or restarts are recorded in logs or process history
  4. Confirm IPv6 is configured
    Execute 'show ipv6 interface brief' to list all configured IPv6 addresses on the device.
    Affected if IPv6 interfaces are configured and reachable on the device (attack requires sending to an IPv6 address)
  5. Check for unexpected device reloads
    Review 'show boot' and 'show logging' for evidence of unexplained reloads or 'system restart' events, particularly correlating with DHCPv6 traffic timestamps.
    Affected if The device has experienced unexpected reloads without clear administrative cause

The device is affected if DHCPv6 relay is enabled, IPv6 is configured, and the NX-OS version is within the vulnerable range, especially if dhcp_snoop crashes or unexplained reloads have occurred.

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 Cisco-provided software update/patch for NX-OS to address this vulnerability. If immediate patching is not possible, consider disabling DHCPv6 relay functionality or restricting IPv6 access to trusted sources via ACLs as a temporary workaround.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
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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-2024-20446 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
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  • Version or environment caveats, and links to real fixes
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