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Secure Firewall Threat DefenseApplication · Cisco

CVE-2020-3577

HIGH · 7.4 CVSS v3.1 Published 2020-10-21
Fix available
A fix is available. Upgrade to 6.3.0.6 / 6.4.0.10 or later.
See remediation →
79/100
Remediation priority · High
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 ingress packet processing path of Cisco Firepower Threat Defense (FTD) Software for interfaces that are configured either as Inline Pair or in Passive mode could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient validation when Ethernet frames are processed. An attacker could exploit this vulnerability by sending malicious Ethernet frames through an affected device. A successful exploit could allow the attacker do either of the following: Fill the /ngfw partition on the device: A full /ngfw partition could result in administrators being unable to log in to the device (including logging in through the console port) or the device being unable to boot up correctly. Note: Manual intervention is required to recover from this situation. Customers are advised to contact the Cisco Technical Assistance Center (TAC) to help recover a device in this condition. Cause a process crash: The process crash would cause the device to reload. No manual intervention is necessary to recover the device after the reload.

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 ingress packet processing path of Cisco Firepower Threat Defense (FTD) Software affects interfaces configured as Inline Pair or Passive mode. Insufficient validation of malicious Ethernet frames allows an adjacent, unauthenticated attacker to either fill the /ngfw partition (causing login/boot failures requiring manual TAC intervention) or trigger a process crash that forces the device to reload.

MitigationApply the Cisco FTD software update addressing CVE-2020-3577. As an interim measure, restrict physical and layer-2 access to affected Inline Pair and Passive interfaces to trusted segments.

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 Threat DefenseApplication
Affected:< 6.3.0.6>= 6.4.0, < 6.4.0.10>= 6.5.0, < 6.5.0.5>= 6.6.0, < 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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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. Identify the FTD software version
    Execute the command 'show version' or 'systemsw version' on the FTD CLI. Look for the version number in the output.
    Affected if The displayed version falls into one of these ranges: < 6.3.0.6; >= 6.4.0 and < 6.4.0.10; >= 6.5.0 and < 6.5.0.5; >= 6.6.0 and < 6.6.1
  2. Confirm interface configuration mode
    Run 'show interface' or 'show running-config | include interface' to list all interface configurations. For each interface, identify whether it is configured as Inline Pair or Passive mode by examining the interface type setting.
    Affected if Any interface is configured as Inline Pair or Passive mode on an affected version
  3. Verify interface assignment to inline set
    If an interface shows as Inline Pair, run 'show inline-set' or 'show running-config | include inline' to confirm the inline set assignment. For Passive mode, run 'show service-policy' to verify the passive interface configuration.
    Affected if The Inline Pair or Passive interface is actively assigned to an inline set or service policy that is in use

You are affected if your FTD version is one of the listed affected versions AND you have interfaces configured as Inline Pair or Passive mode that are actively processing traffic.

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 6.3.0.6 / 6.4.0.10 / 6.5.0.5 or later
Fixed in 6.3.0.66.4.0.106.5.0.5
Interim mitigation

Apply the Cisco FTD software update addressing CVE-2020-3577. As an interim measure, restrict physical and layer-2 access to affected Inline Pair and Passive interfaces to trusted segments.

Fix this in Secure Firewall Threat Defense 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-2020-3577 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