Secure Firewall Threat DefenseApplication · Cisco
CVE-2018-0243
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 detection engine of Cisco Firepower System Software could allow an unauthenticated, remote attacker to bypass a configured file action policy that is intended to drop the Server Message Block Version 2 (SMB2) and SMB Version 3 (SMB3) protocols if malware is detected. The vulnerability is due to incorrect detection of an SMB2 or SMB3 file based on the total file length. An attacker could exploit this vulnerability by sending a crafted SMB2 or SMB3 transfer request through the targeted device. An exploit could allow the attacker to pass SMB2 or SMB3 files that could be malware even though the device is configured to block them. This vulnerability does not exist for SMB Version 1 (SMB1) files. This vulnerability affects Cisco Firepower System Software when one or more file action policies are configured, on software releases prior to 6.2.3. Cisco Bug IDs: CSCvg68807.
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 confidenceThe Cisco Firepower detection engine incorrectly evaluates SMB2 and SMB3 files based on total file length rather than proper protocol detection, allowing malware to bypass file action policies configured to drop these protocols. An unauthenticated remote attacker can send crafted SMB2/SMB3 transfer requests through the device to pass malware that should be blocked. This bypass only affects SMB2/SMB3; SMB1 is not 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
< 6.2.3CVSS 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:3.0/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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Confirm Cisco Firepower Threat Defense is deployedIdentify if the environment includes Cisco Firepower Threat Defense (FTD) as the network security/inspection device. This vulnerability only affects FTD, not other Cisco products.Affected if The product is not Cisco Firepower Threat Defense, then this CVE does not apply.
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Determine the installed Firepower Threat Defense versionAccess the Firepower Management Center or FTD device CLI and retrieve the software version. Compare the version number to the affected range: any version prior to 6.2.3 is vulnerable.Affected if The installed version is less than 6.2.3 and the device inspects SMB2/SMB3 traffic.
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Verify if SMB2/SMB3 file inspection policies are configuredCheck the Firepower file policy configuration to determine whether file action policies are defined for SMB2 or SMB3 protocol traffic. Look for file rules that specify SMB as the application protocol.Affected if File policies exist that target SMB2 or SMB3 traffic - these policies can be bypassed due to the detection flaw.
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Confirm the detection engine is active for SMB trafficVerify that the Firepower detection engine is enabled and actively processing SMB2/SMB3 connections passing through the device. Check if the device is inline or passively monitoring SMB traffic.Affected if The detection engine is actively inspecting SMB2/SMB3 traffic - only then can the bypass be exploited.
A system is affected if it runs Cisco Firepower Threat Defense version lower than 6.2.3 and has file inspection policies configured for SMB2/SMB3 traffic that the detection engine is actively processing.
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 data6.2.3
Upgrade Cisco Firepower System Software to version 6.2.3 or later to remediate the detection engine flaw. Until upgraded, consider implementing additional network-level controls to inspect and block suspicious SMB traffic.
Fix this in Secure Firewall Threat Defense
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-0243 — 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-2018-0243 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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