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Secure Firewall Management CenterApplication · Cisco

CVE-2021-34754

HIGH · 7.5 CVSS v3.1 Published 2021-10-27
Fix available
A fix is available. Upgrade to 6.4.0.13 / 6.6.5.1 or later.
See remediation →
84/100
Remediation priority · High
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
Multiple vulnerabilities in the payload inspection for Ethernet Industrial Protocol (ENIP) traffic for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured rules for ENIP traffic. These vulnerabilities are due to incomplete processing during deep packet inspection for ENIP packets. An attacker could exploit these vulnerabilities by sending a crafted ENIP packet to the targeted interface. A successful exploit could allow the attacker to bypass configured access control and intrusion policies that should be activated for the ENIP packet.

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

Multiple vulnerabilities in Cisco FTD's deep packet inspection for Ethernet Industrial Protocol (ENIP) traffic allow crafted ENIP packets to bypass configured access control and intrusion policies due to incomplete processing during inspection. An unauthenticated remote attacker can exploit this by sending specially constructed ENIP packets to bypass security controls intended to filter or inspect this industrial protocol traffic.

MitigationApply the relevant Cisco FTD software patch for CVE-2021-34754. Until patched, consider implementing additional network segmentation or blocking ENIP traffic at perimeter interfaces as a compensating control.

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
Secure Firewall Management CenterApplication
Affected:= 2.9.12= 2.9.14.0= 2.9.16= 2.9.17= 2.9.18
Secure Firewall Threat DefenseApplication
Affected:>= 6.4.0, < 6.4.0.13>= 6.6.0, < 6.6.5.1>= 6.7.0, < 6.7.0.3>= 7.0.0, < 7.0.1

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
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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. Check Cisco FTD version
    Use the command 'show version' on the FTD device or query the device via FMC to identify the installed FTD software version.
    Affected if The installed version falls within: >= 6.4.0 and < 6.4.0.13, OR >= 6.6.0 and < 6.6.5.1, OR >= 6.7.0 and < 6.7.0.3, OR >= 7.0.0 and < 7.0.1.
  2. Check Cisco Secure Firewall Management Center version
    Log into the FMC web interface or use 'show version' via CLI to identify the FMC software version.
    Affected if The installed version is 2.9.12, 2.9.14.0, 2.9.16, 2.9.17, or 2.9.18.
  3. Verify ENIP inspection configuration
    Check the intrusion policy or access control rules configured on the FTD to determine if EtherNet/IP (ENIP) protocol inspection is enabled or if there are rules targeting ENIP traffic. This can be done via the FMC policy configuration or by examining the running configuration on the FTD device.
    Affected if ENIP deep packet inspection is actively configured in the access control or intrusion policy applied to the network traffic.

A system is affected if it runs an affected version of Cisco FTD or FMC AND has ENIP (EtherNet/IP) inspection enabled in its security policies, allowing specially crafted ENIP packets to bypass those controls.

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
Upgrade available Upgrade to 6.4.0.13 / 6.6.5.1 / 6.7.0.3 or later
Fixed in 6.4.0.136.6.5.16.7.0.3
Interim mitigation

Apply the relevant Cisco FTD software patch for CVE-2021-34754. Until patched, consider implementing additional network segmentation or blocking ENIP traffic at perimeter interfaces as a compensating control.

Recommended fix High confidence

FTD: 6.4.0.13, 6.6.5.1, or 7.0.1 (or later); FMC: 2.9.18 or later

  1. 1. Identify the currently installed Firepower Threat Defense (FTD) version using 'show version' command or via Firepower Management Center
  2. 2. For FTD 6.4.x versions: upgrade to FTD version 6.4.0.13 or later
  3. 3. For FTD 6.6.x versions: upgrade to FTD version 6.6.5.1 or later
  4. 4. For FTD 7.0.x versions: upgrade to FTD version 7.0.1 or later
  5. 5. For Secure Firewall Management Center: upgrade to version 2.9.18 or later
  6. 6. After upgrade, verify the fix by confirming the new version is installed: 'show version'
  7. 7. Test that ENIP traffic is now properly inspected and access control rules are enforced as expected
  8. 8. Review and verify that intrusion policies are triggering correctly for ENIP packets
Caveat Ensure compatibility between FTD and FMC versions before upgrading; review release notes for any changes to ENIP inspection behavior

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

Fix this in Secure Firewall Management Center Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2021-34754 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