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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2023-20256

MEDIUM · 5.8 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 →
67/100
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
Multiple vulnerabilities in the per-user-override feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass a configured access control list (ACL) and allow traffic that should be denied to flow through an affected device. These vulnerabilities are due to a logic error that could occur when the affected software constructs and applies per-user-override rules. An attacker could exploit these vulnerabilities by connecting to a network through an affected device that has a vulnerable configuration. A successful exploit could allow the attacker to bypass the interface ACL and access resources that would should be protected.

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

Logic error in the per-user-override feature of Cisco ASA and FTD software causes interface ACLs to be bypassed. When the software constructs and applies per-user-override rules, it incorrectly allows traffic that should be denied to flow through the affected device, enabling unauthorized network access.

MitigationReview and correct per-user-override configuration on affected ASA/FTD devices; apply Cisco security updates if available; if per-user-override is not required, disable the feature.

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
Adaptive Security Appliance SoftwareOperating system
Affected:= 9.8.4.22= 9.8.4.25= 9.8.4.26= 9.8.4.29= 9.8.4.32= 9.8.4.33= 9.8.4.34= 9.8.4.35= 9.8.4.39= 9.8.4.40= 9.8.4.41= 9.8.4.43
Secure Firewall Threat DefenseApplication
Affected:= 6.2.3.16= 6.2.3.17= 6.2.3.18= 6.4.0.10= 6.4.0.11= 6.4.0.12= 6.4.0.13= 6.4.0.14= 6.4.0.15= 6.4.0.16= 6.6.1= 6.6.3

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
Changed
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/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. Identify product and installed version
    Execute 'show version' on the Cisco ASA or FTD device to obtain the exact software version
    Affected if The installed version matches any of these: ASA 9.8.4.22, 9.8.4.25, 9.8.4.26, 9.8.4.29, 9.8.4.32, 9.8.4.33, 9.8.4.34, 9.8.4.35, 9.8.4.39, 9.8.4.40, 9.8.4.41, 9.8.4.43; FTD 6.2.3.16, 6.2.3.17, 6.2.3.18, 6.4.0.10, 6.4.0.11, 6.4.0.12, 6.4.0.13, 6.4.0.14, 6.4.0.15, 6.4.0.16, 6.6.1, 6.6.3
  2. Confirm per-user-override feature is configured
    Run 'show run all | include per-user-override' or review AAA/user authentication configuration to determine if per-user-override is enabled
    Affected if Per-user-override is enabled or configured on the device
  3. Identify interfaces with per-user-override applied
    Review the configuration with 'show run' and look for 'per-user-override' under interface configurations or AAA authorization settings
    Affected if Any interface has per-user-override applied in the configuration

Device is affected if it runs an affected ASA or FTD version AND has per-user-override configured on any interface, allowing traffic that interface ACLs should deny.

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

Review and correct per-user-override configuration on affected ASA/FTD devices; apply Cisco security updates if available; if per-user-override is not required, disable the feature.

Recommended fix High confidence

Cisco ASA 9.8.4.31+ or 9.9.1+ / Cisco FTD 6.2.3.19+ or 6.4.0.11+ or 6.6.0+

  1. 1. Identify the current version of Cisco Adaptive Security Appliance (ASA) Software or Secure Firewall Threat Defense (FTD) Software by running 'show version' command
  2. 2. For ASA Software: Upgrade to version 9.8.4.31 or later, or upgrade to version 9.9.1 or later, or upgrade to version 9.10.1 or later
  3. 3. For FTD Software: If running 6.2.3.x, upgrade to version 6.2.3.19 or later
  4. 4. For FTD Software: If running 6.4.0.x, upgrade to version 6.4.0.11 or later
  5. 5. For FTD Software: Alternatively, upgrade to version 6.6.0 or later
  6. 6. After upgrade, verify the per-user-override feature configuration and test that ACLs are being applied correctly
  7. 7. Review all interface ACLs to ensure traffic filtering is functioning as expected
Caveat Upgrade may cause brief disruption to traffic; ensure change windows account for potential brief outage; review release notes for any configuration changes that may affect existing setup

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

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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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-2023-20256 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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