Secure Firewall Management CenterApplication · Cisco
CVE-2016-6439
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 reassembly of HTTP packets for Cisco Firepower System Software before 6.0.1 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to the Snort process unexpectedly restarting. The vulnerability is due to improper handling of an HTTP packet stream. An attacker could exploit this vulnerability by sending a crafted HTTP packet stream to the detection engine on the targeted device. An exploit could allow the attacker to cause a DoS condition if the Snort process restarts and traffic inspection is bypassed or traffic is 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 confidenceA vulnerability in Cisco Firepower's Snort detection engine HTTP packet reassembly allows an unauthenticated remote attacker to cause a denial of service by sending a crafted HTTP packet stream that triggers an unexpected Snort process restart. This can result in traffic inspection being bypassed or traffic being dropped.
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 Management CenterApplication
= 5.3.0= 5.3.0.2= 5.3.0.3= 5.3.0.4= 5.3.1= 5.3.1.3= 5.3.1.4= 5.3.1.5= 5.3.1.6= 5.4.0= 5.4.0.2= 5.4.1CVSS 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
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/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 Cisco Secure Firewall Management Center versionAccess the FMC web interface and navigate to System > Updates, or use the CLI command 'show version' on the management center appliance to display the installed software version.Affected if The displayed version matches any of these: 5.3.0, 5.3.0.2, 5.3.0.3, 5.3.0.4, 5.3.1, 5.3.1.3, 5.3.1.4, 5.3.1.5, 5.3.1.6, 5.4.0, 5.4.0.2, or 5.4.1.
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Confirm Snort detection engine is activeIn the FMC web interface, go to Policies > Access Control Policy, select your policy, and verify that an Intrusion Policy with Snort-based inspection is attached and enabled.Affected if Snort-based intrusion inspection is enabled and the policy is deployed to managed devices.
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Verify HTTP traffic inspection is configuredIn the FMC, navigate to Policies > Intrusion Policy > Advanced Settings > HTTP Preprocessor, or inspect the Snort configuration files on the managed device under /var/sf/Running/ for http_inspect settings.Affected if HTTP packet reassembly is enabled in the Snort configuration, which is the default setting.
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Check for recent Snort process restartsOn the managed Firepower device CLI, run 'show process' or check system logs with 'grep -i snort /var/log/*.log' for unexpected Snort process restarts or crashes.Affected if Snort processes are restarting unexpectedly without explicit administrative action.
You are affected if the Cisco Secure Firewall Management Center runs any of the listed versions (5.3.x or 5.4.x) with Snort-based HTTP inspection enabled, as the vulnerability triggers Snort process restarts when crafted HTTP packets are processed.
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 dataUpgrade Cisco Firepower System Software to version 6.0.1 or later to remediate this vulnerability.
Fix this in Secure Firewall Management Center
Scoped from the published advisory
- Consultation4.0 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 $4,544.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-6439 — 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-2016-6439 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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