Adaptive Security ApplianceApplication · Cisco
CVE-2020-3306
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 · uneditedA vulnerability in the DHCP module of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. The vulnerability is due to incorrect processing of certain DHCP packets. An attacker could exploit this vulnerability by sending a crafted DHCP packet to the affected device. A successful exploit could allow the attacker to cause a DoS condition on the affected 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 · high confidenceA vulnerability in the DHCP module of Cisco ASA and FTD software allows an unauthenticated remote attacker to cause denial of service by sending specially crafted DHCP packets to the affected device. The vulnerability stems from incorrect processing of certain DHCP packets.
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 ApplianceApplication
< 9.6.4.34
Adaptive Security Appliance SoftwareOperating system
>= 9.7, < 9.8.4.10>= 9.9, < 9.10.1.30>= 9.12, < 9.12.3
Secure Firewall Threat DefenseApplication
< 6.3.0.5>= 6.4.0, < 6.4.0.4CVSS 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
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/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 checksWork through these to decide whether this CVE applies to you.
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Identify the product and versionRun 'show version' on the ASA or FTD device CLI to obtain the software versionAffected if The displayed version falls within any of these ranges: ASA < 9.6.4.34; ASA 9.7.x to < 9.8.4.10; ASA 9.9.x to < 9.10.1.30; ASA 9.12.x to < 9.12.3; FTD < 6.3.0.5; FTD 6.4.0.x to < 6.4.0.4
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Confirm DHCP server or relay is configuredRun 'show run all service-policy | include dhcp' or 'show run | include dhcp' to check for DHCP server (dhcpd) or DHCP relay (dhcp-relay) configurationAffected if DHCP server or DHCP relay is enabled on the device - this exposes the vulnerable DHCP processing code
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Verify DHCP is bound to an interfaceRun 'show run dhcpd' to see which interfaces have DHCP services bound and their configurationAffected if DHCP services are bound to any interface, particularly outside/internet-facing interfaces where malicious DHCP packets could be received
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Check network exposure of DHCP serviceReview interface security levels and access lists using 'show run interface' and 'show access-list' to determine if DHCP traffic from untrusted networks can reach the deviceAffected if The device's DHCP service is reachable from untrusted networks without proper filtering at network boundaries
You are affected if your device runs a Cisco ASA or FTD version within the affected ranges AND has DHCP server or relay enabled and exposed to potentially malicious DHCP traffic.
Generated from the published advisory. Verify against your own configuration.
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 data6.3.0.56.4.0.49.6.4.34
Apply the vendor-provided security patches for Cisco ASA and FTD software. Until patched, consider filtering or rate-limiting DHCP traffic at network boundaries.
Fix this in Adaptive Security Appliance
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3306 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-3306 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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