dbcve.org
Secure Firewall Threat DefenseApplication · Cisco

CVE-2023-20031

MEDIUM · 5.4 CVSS v3.1 Published 2023-11-01
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
63/100
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 SSL/TLS certificate handling of Snort 3 Detection Engine integration with Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 detection engine to restart. This vulnerability is due to a logic error that occurs when an SSL/TLS certificate that is under load is accessed when it is initiating an SSL connection. Under specific, time-based constraints, an attacker could exploit this vulnerability by sending a high rate of SSL/TLS connection requests to be inspected by the Snort 3 detection engine on an affected device. A successful exploit could allow the attacker to cause the Snort 3 detection engine to reload, resulting in either a bypass or a denial of service (DoS) condition, depending on device configuration. The Snort detection engine will restart automatically. No manual intervention is required.

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 logic error in the Snort 3 detection engine's SSL/TLS certificate handling within Cisco Firepower Threat Defense causes the engine to restart when certificates are accessed during SSL connection initiation under specific time-based constraints. An unauthenticated remote attacker can trigger this by sending a high rate of SSL/TLS connection requests to be inspected, resulting in either traffic bypass or denial of service depending on device configuration.

MitigationApply the vendor-provided patches for Cisco FTD software. In the interim, evaluate device configuration to minimize bypass impact if Snort reloads occur, and consider rate limiting SSL/TLS traffic where feasible to reduce exploit feasibility.

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:= 6.7.0= 6.7.0.1= 6.7.0.2= 6.7.0.3= 7.0.0= 7.0.0.1= 7.0.1= 7.0.1.1= 7.0.2= 7.0.2.1= 7.0.3= 7.0.4

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
Changed
Confidentiality
None
Integrity
Low
Availability
Low

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

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. Verify FTD software version
    Run 'show version' or check the FTD management interface to determine the installed Cisco Firepower Threat Defense version.
    Affected if The installed version matches one of these: 6.7.0, 6.7.0.1, 6.7.0.2, 6.7.0.3, 7.0.0, 7.0.0.1, 7.0.1, 7.0.1.1, 7.0.2, 7.0.2.1, 7.0.3, or 7.0.4.
  2. Confirm Snort 3 detection engine is active
    Access FTD CLI and run 'show snort3' or check the intrusion policy settings to verify Snort 3 is the active detection engine.
    Affected if Snort 3 is the active detection engine in use on the device.
  3. Verify SSL/TLS inspection is enabled
    Review the access control policy or intrusion policy configuration via FTD management interface or CLI to determine if SSL/TLS inspection rules are active.
    Affected if SSL/TLS inspection or decryption policies are configured and applied to traffic.
  4. Check for Snort engine restart events
    Review system logs, audit logs, or run 'show snort3 statistics' to identify recent Snort engine reloads or restarts that correlate with high SSL/TLS traffic periods.
    Affected if Snort engine restarts or reloads are occurring without other known causes.

Environment is affected if running an affected FTD version with Snort 3 active and SSL/TLS inspection enabled, especially if unexplained Snort restarts are observed.

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 the vendor-provided patches for Cisco FTD software. In the interim, evaluate device configuration to minimize bypass impact if Snort reloads occur, and consider rate limiting SSL/TLS traffic where feasible to reduce exploit feasibility.

Recommended fix Moderate confidence

Secure Firewall Threat Defense 6.7.0.4 or later (or 6.8.0+)

  1. 1. Identify current Secure Firewall Threat Defense version using 'show version' command
  2. 2. Verify the device is running an affected version (6.7.0, 6.7.0.1, 6.7.0.2, or 6.7.0.3)
  3. 3. Schedule a maintenance window for the upgrade operation
  4. 4. Download the fixed FTD software image from Cisco (version 6.7.0.4 or later, or 6.8.0+)
  5. 5. Upload the new image to the device using 'upgrade' or FMC interface
  6. 6. Install the upgrade and verify the Snort 3 engine loads successfully
  7. 7. Confirm the new version is running with 'show version'
  8. 8. Verify Snort 3 inspection is operational with 'show module snort'
Caveat Major version upgrades (e.g., 6.7 to 6.8) may require compatibility checks with FMC and could change behavior; review Cisco release notes for any configuration or feature changes

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

Fix this in Secure Firewall Threat Defense 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-2023-20031 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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