dbcve.org
Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2023-20081

MEDIUM · 5.9 CVSS v3.1 Published 2023-03-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
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 IPv6 DHCP (DHCPv6) client module of Cisco Adaptive Security Appliance (ASA) Software, Cisco Firepower Threat Defense (FTD) Software, Cisco IOS Software, and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient validation of DHCPv6 messages. An attacker could exploit this vulnerability by sending crafted DHCPv6 messages to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. Note: To successfully exploit this vulnerability, the attacker would need to either control the DHCPv6 server or be in a man-in-the-middle position.

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 is a vulnerability in the IPv6 DHCP (DHCPv6) client module of Cisco ASA, FTD, IOS, and IOS XE Software. The vulnerability stems from insufficient validation of DHCPv6 messages, allowing an attacker who controls the DHCPv6 server or occupies a man-in-the-middle position to send crafted DHCPv6 messages that cause the affected device to reload, resulting in denial of service.

MitigationApply the relevant Cisco security patches for ASA, FTD, IOS, and IOS XE Software when available. Additionally, restrict DHCPv6 traffic to trusted servers using network access controls and monitor for unexpected DHCPv6 traffic.

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:= 9.8.1= 9.8.1.5= 9.8.1.7= 9.8.2= 9.8.2.8= 9.8.2.14= 9.8.2.15= 9.8.2.17= 9.8.2.20= 9.8.2.24= 9.8.2.26= 9.8.2.28
Secure Firewall Threat DefenseApplication
Affected:= 9.8.1= 9.8.1.5= 9.8.1.7= 9.8.2= 9.8.2.8= 9.8.2.14= 9.8.2.15= 9.8.2.17= 9.8.2.20= 9.8.2.24= 9.8.2.26= 9.8.2.28
iOSOperating system
Affected:= 17.8.1
Ios XeOperating system
Affected:= 17.8.1

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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 device product and software version
    Run 'show version' or 'show inventory' on the device CLI to determine if it is Cisco ASA, FTD, iOS, or iOS XE and note the exact software version number
    Affected if The device runs ASA, FTD, iOS, or iOS XE version 9.8.1 through 9.8.2.28 (ASA/FTD), 17.8.1 (iOS/iOS XE), or another version that matches the affected range listed in the CVE advisory
  2. Verify IPv6 is enabled on the device
    Run 'show ipv6 interface brief' or 'show running-config | include ipv6' to check if IPv6 is configured
    Affected if IPv6 is enabled and the device software version is in the affected list
  3. Confirm DHCPv6 client is configured
    Run 'show running-config | include dhcpv6' or check interface configurations with 'show ipv6 dhcp interface' to see if DHCPv6 client requests are enabled on any interface
    Affected if DHCPv6 client is actively requesting or processing DHCPv6 messages on any interface and the software version is affected
  4. Check for DHCPv6 server trust status
    Review access control lists or IPv6 traffic filters with 'show access-list' or 'show ipv6 traffic' to determine if DHCPv6 traffic is restricted to trusted servers
    Affected if DHCPv6 traffic is not restricted (no ACL filtering DHCPv6 port 547) and the device is on an accessible network segment where an attacker could inject malicious DHCPv6 messages

The device is affected if it runs a vulnerable ASA, FTD, iOS, or iOS XE version (9.8.1-9.8.2.28 for ASA/FTD, 17.8.1 for iOS/iOS XE) AND has IPv6 with DHCPv6 client enabled, and an attacker could send crafted DHCPv6 messages to trigger the denial of service.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the relevant Cisco security patches for ASA, FTD, IOS, and IOS XE Software when available. Additionally, restrict DHCPv6 traffic to trusted servers using network access controls and monitor for unexpected DHCPv6 traffic.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,260
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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-2023-20081 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