Secure Firewall Threat DefenseApplication · Cisco
CVE-2021-1504
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 · uneditedMultiple vulnerabilities in Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. These vulnerabilities are due to lack of proper input validation of the HTTPS request. An attacker could exploit these vulnerabilities by sending a crafted HTTPS request to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Note: This vulnerability affects only specific AnyConnect and WebVPN configurations. For more information, see the Vulnerable Products section.
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 confidenceMultiple vulnerabilities in Cisco ASA and FTD software allow unauthenticated remote attackers to cause denial of service by sending crafted HTTPS requests to affected devices. The vulnerabilities stem from improper input validation of HTTPS traffic. Successful exploitation forces the affected device to reload, disrupting VPN services. Only devices with specific AnyConnect or WebVPN configurations are affected.
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
>= 6.5.0, < 6.6.4>= 6.7.0, < 6.7.0.1
Adaptive Security Appliance SoftwareOperating system
>= 9.7, < 9.8.4.35>= 9.9, < 9.9.2.85>= 9.10, < 9.12.4.10>= 9.13, < 9.13.1.21>= 9.14, < 9.14.2.4>= 9.15, < 9.15.1.7CVSS 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 Cisco device type and versionRun 'show version' on the device CLI. Look for 'Cisco Adaptive Security Appliance Software' or 'Cisco Firepower Threat Defense' and note the software version number displayed.Affected if The device runs ASA software version within any of these ranges: >= 9.7 and < 9.8.4.35, >= 9.9 and < 9.9.2.85, >= 9.10 and < 9.12.4.10, >= 9.13 and < 9.13.1.21, >= 9.14 and < 9.14.2.4, >= 9.15 and < 9.15.1.7; OR FTD software version >= 6.5.0 and < 6.6.4, or >= 6.7.0 and < 6.7.0.1.
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Verify if AnyConnect VPN is enabledRun 'show run webvpn' and 'show run anyconnect' (ASA) or check the FTD management interface for AnyConnect configuration. Look for any active anyconnect-*. AnyConnect profiles or sslvpn enable commands in the configuration.Affected if AnyConnect client access is configured and enabled on the device.
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Verify if WebVPN is enabledRun 'show run webvpn' (ASA) and look for 'webvpn enable' or 'webvpn' configuration blocks. On FTD, check the SSL VPN or WebVPN policy configuration.Affected if WebVPN (also known as SSL VPN) is enabled and accessible.
The device is affected if it runs a vulnerable ASA or FTD version AND has either AnyConnect or WebVPN functionality enabled, as these are the only attack vectors for this CVE.
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 data6.6.46.7.0.19.8.4.35
Apply Cisco security patches for ASA and FTD software. As an interim measure, restrict or disable AnyConnect and WebVPN access to trusted sources only until patches can be deployed.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1504 — 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-2021-1504 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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