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Content Security Management ApplianceApplication · Cisco

CVE-2016-6416

MEDIUM · 5.9 CVSS v3.0 Published 2016-10-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
The FTP service in Cisco AsyncOS on Email Security Appliance (ESA) devices 9.6.0-000 through 9.9.6-026, Web Security Appliance (WSA) devices 9.0.0-162 through 9.5.0-444, and Content Security Management Appliance (SMA) devices allows remote attackers to cause a denial of service via a flood of FTP traffic, aka Bug IDs CSCuz82907, CSCuz84330, and CSCuz86065.

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 confidence

The FTP service in Cisco AsyncOS on Email Security Appliance (ESA), Web Security Appliance (WSA), and Content Security Management Appliance (SMA) devices contains a vulnerability that allows remote attackers to cause denial of service by flooding the device with excessive FTP traffic, causing service disruption.

MitigationApply Cisco software updates (patches) for the specific AsyncOS versions. As a temporary workaround, implement network-level rate limiting or access control lists to restrict or throttle FTP traffic to affected devices.

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
Content Security Management ApplianceApplication
Affected:= 9.1.0= 9.1.0-004= 9.1.0-031= 9.1.0-033= 9.1.0-103= 9.5.0= 9.6.0
Email Security ApplianceApplication
Affected:= 9.6.0-000= 9.6.0-042= 9.6.0-051= 9.7.1-066= 9.9.6-026= 9.9_base
Web Security ApplianceApplication
Affected:= 9.0.0-162= 9.1.0-000= 9.1.0-070= 9.1_base= 9.5.0-235= 9.5.0-284= 9.5.0-444= 9.5_base

CVSS 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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the appliance model
    Log into the device CLI and run 'show hardware' or check the web interface header for the appliance type (ESA, WSA, or SMA)
    Affected if The device is a Cisco Email Security Appliance, Web Security Appliance, or Content Security Management Appliance
  2. Check the AsyncOS version
    Run the CLI command 'version' or 'show version' to display the installed AsyncOS version and build number
    Affected if The displayed version matches any of the specific versions listed for ESA, WSA, or SMA in the affected products list
  3. Verify FTP service is enabled
    In the web interface, go to Network > IP Interfaces or use CLI command 'list' to see enabled services; check if FTP listener is configured under Network > FTP Proxy or Services
    Affected if FTP service is enabled and listening on any interface (the vulnerability requires the FTP service to be exposed)
  4. Check FTP traffic exposure
    Review firewall rules or ACLs to determine if the device FTP port (port 21 by default) is reachable from untrusted networks
    Affected if FTP port is accessible from external or untrusted networks, allowing remote attackers to flood with traffic

The environment is affected if the device is an ESA, WSA, or SMA running an AsyncOS version that matches the specific build numbers listed, and the FTP service is enabled and network-accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco software updates (patches) for the specific AsyncOS versions. As a temporary workaround, implement network-level rate limiting or access control lists to restrict or throttle FTP traffic to affected devices.

Fix this in Content Security Management Appliance Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-6416 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data