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Permissions, Privileges & Access ControlsWeakness · CWE-264

CVE-2024-20371

MEDIUM · 5.3 CVSS v3.1 Published 2024-11-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
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 access control list (ACL) programming of Cisco Nexus 3550-F Switches could allow an unauthenticated, remote attacker to send traffic that should be blocked to the management interface of an affected device.  This vulnerability exists because ACL deny rules are not properly enforced at the time of device reboot. An attacker could exploit this vulnerability by attempting to send traffic to the management interface of an affected device. A successful exploit could allow the attacker to send traffic to the management interface of the affected device.

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 · moderate confidence

A vulnerability in the ACL programming of Cisco Nexus 3550-F Switches allows unauthenticated remote attackers to send traffic to the management interface that should be blocked. The root cause is that ACL deny rules are not properly enforced at the time of device reboot, creating a window where management interface access controls fail.

MitigationApply the vendor patch when available. In the interim, use upstream network filtering (firewalls/ACLs on adjacent devices) to restrict access to the management interface, and consider network segmentation to limit exposure.

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
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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

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 device model
    Run 'show inventory' or 'show version' and look for 'Nexus 3550-F' in the output
    Affected if The device is not a Cisco Nexus 3550-F Switch, then it is not affected by this specific CVE
  2. Check the installed software version
    Run 'show version' and locate the 'NXOS' or 'system version' line. Compare this version against the Cisco advisory for CVE-2024-20371 to see if it falls within the affected version range
    Affected if The software version is within the range that Cisco has identified as vulnerable to CVE-2024-20371
  3. Verify ACL configuration on management interface
    Run 'show running-config interface mgmt0' to view the management interface configuration. Check for any ACL applied with 'ip access-group' statements
    Affected if No ACL is applied to the management interface, then this specific ACL bypass condition does not apply to your configuration
  4. Check for ACL deny rules targeting management traffic
    Run 'show ip access-lists' and examine any ACL applied to mgmt0. Look for 'deny' rules that should block unauthorized management access
    Affected if No deny rules exist in the ACL for the management interface, then there is no rule that could fail to be enforced during reboot
  5. Check device uptime and recent reboot events
    Run 'show system uptime' or 'show version' to see device uptime. A recent reboot indicates the window where ACL enforcement may have been incomplete
    Affected if The device has been recently rebooted and has an ACL with deny rules on mgmt0, the ACL may have been in a bypassed state during the post-reboot window

You are affected if you have a Cisco Nexus 3550-F Switch running a software version within the vulnerable range, with an ACL containing deny rules applied to the management interface, especially if the device has recently rebooted.

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 vendor patch when available. In the interim, use upstream network filtering (firewalls/ACLs on adjacent devices) to restrict access to the management interface, and consider network segmentation to limit exposure.

Have this fixed 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-2024-20371 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
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