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Firepower Extensible Operating SystemOperating system · Cisco

CVE-2024-20294

MEDIUM · 6.6 CVSS v3.1 Published 2024-02-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
69/100
Remediation priority · Elevated
No privileges

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 Link Layer Discovery Protocol (LLDP) feature of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of specific fields in an LLDP frame. An attacker could exploit this vulnerability by sending a crafted LLDP packet to an interface of an affected device and having an authenticated user retrieve LLDP statistics from the affected device through CLI show commands or Simple Network Management Protocol (SNMP) requests. A successful exploit could allow the attacker to cause the LLDP service to crash and stop running on the affected device. In certain situations, the LLDP crash may result in a reload of the affected device. Note: LLDP is a Layer 2 link protocol. To exploit this vulnerability, an attacker would need to be directly connected to an interface of an affected device, either physically or logically (for example, through a Layer 2 Tunnel configured to transport the LLDP protocol).

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 Cisco FXOS and NX-OS LLDP implementation allows an adjacent unauthenticated attacker to cause denial of service by sending a crafted LLDP packet. The attack requires an authenticated user to subsequently retrieve LLDP statistics via CLI or SNMP to trigger the condition, causing the LLDP service to crash and potentially forcing a device reload.

MitigationApply Cisco security patches for FXOS and NX-OS when available. Consider disabling LLDP on untrusted interfaces or implementing network access controls to restrict LLDP traffic to trusted adjacent devices only.

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
Firepower Extensible Operating SystemOperating system
Affected:= 2.2.1.63= 2.2.1.66= 2.2.1.70= 2.2.2.17= 2.2.2.19= 2.2.2.24= 2.2.2.26= 2.2.2.28= 2.2.2.54= 2.2.2.60= 2.2.2.71= 2.2.2.83
Nx OsOperating system
Affected:= 12.0\(1m\)= 12.0\(1n\)= 12.0\(1o\)= 12.0\(1p\)= 12.0\(1q\)= 12.0\(1r\)= 12.0\(2f\)= 12.0\(2g\)= 12.0\(2h\)= 12.0\(2l\)= 12.0\(2m\)= 12.0\(2n\)
Unified Computing SystemApplication
Affected:= 3.1\(1e\)= 3.1\(1g\)= 3.1\(1h\)= 3.1\(1k\)= 3.1\(1l\)= 3.1\(2b\)= 3.1\(2c\)= 3.1\(2d\)= 3.1\(2e\)= 3.1\(2f\)= 3.1\(2g\)= 3.1\(2h\)

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

CVSS:3.1/AV:A/AC:L/PR:N/UI:R/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. Identify device OS and version
    Run `show version` on the device CLI to obtain the exact software version. For FXOS, also run `show fxos version` if available.
    Affected if The displayed version matches one of the affected versions listed in the CVE (e.g., FXOS 2.2.2.83, NX-OS 12.0(2n), UCS 3.1(2h))
  2. Confirm LLDP is enabled
    Run `show lldp` or `show lldp neighbors` to verify LLDP is currently enabled and functioning on the device.
    Affected if LLDP is enabled and running (the vulnerability only affects systems where LLDP is active)
  3. Check for recent LLDP-related crashes
    Run `show logging | include LLDP` or `show process log` to look for LLDP process crash messages or restarts.
    Affected if Recent crash logs indicate LLDP service failures or unexpected process restarts since the CVE publication date
  4. Verify system uptime and reload history
    Run `show version` to check system uptime and `show reload` or `show crashlog` to review recent reload reasons.
    Affected if The device has reloaded unexpectedly or shows crash information tied to LLDP since the vulnerability window
  5. Check SNMP LLDP statistics access
    Review SNMP configuration with `show snmp` and verify if any authenticated users have access to LLDP OIDs (1.0.8802.1.1.2).
    Affected if SNMP is enabled with LLDP statistics accessible to authenticated users, which would allow triggering the condition described in the CVE

A device is likely affected if it runs an affected FXOS, NX-OS, or UCS version AND has LLDP enabled, particularly if LLDP crashes or unexplained reloads have occurred after receiving crafted LLDP packets from adjacent devices.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco security patches for FXOS and NX-OS when available. Consider disabling LLDP on untrusted interfaces or implementing network access controls to restrict LLDP traffic to trusted adjacent devices only.

Recommended fix Moderate confidence

Contact Cisco for product-specific fixed releases (advisory CSCwj74490 on sec.cloudapps.cisco.com)

  1. 1. Identify the specific Cisco product (FXOS, NX-OS, or UCS) and current affected version running on the device
  2. 2. Contact Cisco Technical Support or check the Cisco Security Advisory page at sec.cloudapps.cisco.com for this specific CVE
  3. 3. Request and obtain the recommended fixed release for your specific product version
  4. 4. Plan maintenance window as the upgrade may require device reload
  5. 5. Before upgrading, back up current device configuration
  6. 6. Upgrade the device to the Cisco-recommended fixed release that addresses CVE-2024-20294
  7. 7. After upgrade, verify LLDP service is running: execute 'show lldp' and confirm no crashes occur
  8. 8. Verify the new version is no longer vulnerable by confirming the LLDP process stability
Caveat Some upgrades may require code train migration; ensure compatibility with existing infrastructure before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firepower Extensible Operating System Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing3.0 h
  • Review / QA2.0 h
17.0 hours of engineering $3,050
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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-2024-20294 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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