Secure Firewall Threat DefenseApplication · Cisco
CVE-2020-3285
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 Transport Layer Security version 1.3 (TLS 1.3) policy with URL category functionality for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass a configured TLS 1.3 policy to block traffic for a specific URL. The vulnerability is due to a logic error with Snort handling of the connection with the TLS 1.3 policy and URL category configuration. An attacker could exploit this vulnerability by sending crafted TLS 1.3 connections to an affected device. A successful exploit could allow the attacker to bypass the TLS 1.3 policy and access URLs that are outside the affected device and normally would be dropped.
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 confidenceIn Cisco Firepower Threat Defense, a logic error in Snort's handling of TLS 1.3 connections combined with URL category policy configuration allows attackers to bypass configured blocks. Specifically, when TLS 1.3 policies are set to block certain URL categories, the affected device fails to properly inspect and drop connections to those URLs, permitting access to blocked content.
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
>= 6.4.0, <= 6.4.0.8CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check FTD software versionRun 'show version' on the FTD device or check the version via Firepower Management Center. Look for the specific version number in the 6.4.0.x line.Affected if The installed version is 6.4.0 through 6.4.0.8 inclusive.
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Verify TLS 1.3 policy is enabledAccess the SSL/SSH inspection policy in Firepower Management Center or via CLI 'show snort ssl inspecting' and confirm TLS 1.3 protocol version is enabled in the TLS policy settings.Affected if TLS 1.3 is enabled in the Snort SSL inspection policy.
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Identify URL category blocking rulesReview the access control policy applied to the FTD device. Check for any rules that block traffic based on URL categories (such as malware, phishing, or custom categories). Use 'show url-filtering category' or view via FMC policy configuration.Affected if Access control rules are configured to block specific URL categories.
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Confirm TLS inspection is applied to blocked URL trafficExamine the policy configuration to verify that TLS inspection (especially TLS 1.3) is being applied to the same traffic flows where URL category blocking is configured. Check that the access control rule action is 'Block' and TLS inspection is enabled for that rule.Affected if A rule exists that both enables TLS 1.3 inspection and blocks traffic based on URL category, with both features applied to the same traffic.
You are affected if your FTD version is 6.4.0 through 6.4.0.8 and you have TLS 1.3 enabled combined with URL category blocking policies applied to inspect that 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 dataApply the Cisco-provided software update for FTD when available. As an interim measure, consider using TLS 1.2 policies or additional filtering methods to restrict access to sensitive URL categories until the patch can be deployed.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3285 — 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-2020-3285 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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- Version or environment caveats, and links to real fixes
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