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Secure Firewall Management CenterApplication · Cisco

CVE-2020-3549

HIGH · 8.1 CVSS v3.1 Published 2020-10-21
Fix available
A fix is available. Upgrade to 6.6.1 or later.
See remediation →
90/100
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 sftunnel functionality of Cisco Firepower Management Center (FMC) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to obtain the device registration hash. The vulnerability is due to insufficient sftunnel negotiation protection during initial device registration. An attacker in a man-in-the-middle position could exploit this vulnerability by intercepting a specific flow of the sftunnel communication between an FMC device and an FTD device. A successful exploit could allow the attacker to decrypt and modify the sftunnel communication between FMC and FTD devices, allowing the attacker to modify configuration data sent from an FMC device to an FTD device or alert data sent from an FTD device to an FMC 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

This vulnerability in Cisco FMC and FTD software's sftunnel functionality allows an unauthenticated remote attacker with MITM positioning to intercept the initial device registration negotiation and obtain the device registration hash. With this hash, the attacker can decrypt and modify sftunnel communications, potentially altering configuration data from FMC to FTD or alert data from FTD to FMC.

MitigationApply Cisco security updates when available; ensure network segmentation and topology prevents unauthorized MITM positioning between FMC and FTD devices; consider implementing additional certificate-based authentication controls for sftunnel communications.

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:< 6.6.1
Secure Firewall Threat DefenseApplication
Affected:< 6.6.1

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

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 Cisco FMC or FTD version
    Run 'show version' on the device CLI or check the FMC web interface under System > About > Version
    Affected if The displayed version is below 6.6.1 (for example, 6.5.0, 6.4.0, 6.3.0)
  2. Confirm FMC-FTD deployment exists
    On FMC, navigate to Devices > Device Management to list registered FTD devices. On FTD, run 'show managers' to confirm connection to an FMC.
    Affected if Any FTD device is registered to an FMC, establishing an sftunnel between them
  3. Check sftunnel status on FTD
    On the FTD CLI, run 'show sftunnel' or 'show star-config' to verify the sftunnel connection to FMC is active
    Affected if The sftunnel connection to FMC shows as 'up' or 'connected'
  4. Verify network topology for MITM exposure
    Review network paths between FMC and FTD devices. Check if any untrusted network segments, switches, or VPN concentrators exist between them that an attacker could intercept.
    Affected if The FMC and FTD communicate across network segments not fully under your administrative control, or across shared/internet-facing infrastructure

You are affected if your FMC or FTD version is below 6.6.1 AND you have an active FMC-FTD registration using sftunnel, with potential for an attacker to intercept traffic between them.

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
Upgrade available Upgrade to 6.6.1 or later
Fixed in 6.6.1
Interim mitigation

Apply Cisco security updates when available; ensure network segmentation and topology prevents unauthorized MITM positioning between FMC and FTD devices; consider implementing additional certificate-based authentication controls for sftunnel communications.

Fix this in Secure Firewall Management Center Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing16.0 h
  • Review / QA8.0 h
56.0 hours of engineering $9,760
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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-2020-3549 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