Secure Firewall Threat DefenseApplication · Cisco
CVE-2020-3299
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 Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured File Policy for HTTP. The vulnerability is due to incorrect detection of modified HTTP packets used in chunked responses. An attacker could exploit this vulnerability by sending crafted HTTP packets through an affected device. A successful exploit could allow the attacker to bypass a configured File Policy for HTTP packets and deliver a malicious payload.
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 confidenceThis vulnerability in Cisco's Snort detection engine allows attackers to bypass configured HTTP File Policies by sending crafted HTTP packets with modified chunked responses. The issue stems from incorrect handling of chunked transfer encoding in HTTP responses, enabling malicious files to pass through without inspection.
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
>= 6.0.0, < 6.3.0.1< 2.9.13.1CVSS 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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Identify Cisco FTD versionUse the command 'show version' or check the FTD management interface for the installed Firepower Threat Defense versionAffected if The installed version is >= 6.0.0 and < 6.3.0.1
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Identify Snort engine versionUse the command 'show snort version' or check the snort binary version on the FTD device if accessibleAffected if The Snort version is earlier than 2.9.13.1
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Confirm HTTP File Policy is activeCheck the Firepower management console for configured File Policies under Policies > File Policies, and verify if HTTP file inspection is enabled in the access control policyAffected if An HTTP File Policy is configured and applied to traffic inspection
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Verify chunked transfer encoding inspectionReview Snort HTTP inspector logs or enable debug logging to observe how chunked transfer encoding is being handled in HTTP responsesAffected if Chunked HTTP responses are being processed by the Snort inspection engine without proper chunk size validation
You are affected if your Cisco FTD runs version 6.0.0 through 6.3.0.0 (or Snort < 2.9.13.1) AND you have an HTTP File Policy enabled for traffic inspection.
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 data2.9.13.16.3.0.1
Apply the vendor-supplied patches for affected Cisco products. Verify that the File Policy for HTTP is functioning correctly after patching by testing with sample malicious HTTP payloads.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 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 $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3299 — 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-2020-3299 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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