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Ace Application Control Engine Module A1Plugin / extension · Cisco

CVE-2016-6399

HIGH · 7.5 CVSS v3.0 Published 2016-09-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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
Cisco ACE30 Application Control Engine Module through A5 3.3 and ACE 4700 Application Control Engine appliances through A5 3.3 allow remote attackers to cause a denial of service (device reload) via crafted (1) SSL or (2) TLS packets, aka Bug ID CSCvb16317.

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 confidence

A denial of service vulnerability in Cisco ACE30 Application Control Engine Module and ACE 4700 appliances allows remote attackers to cause device reload by sending crafted SSL or TLS packets. The vulnerability exists in software versions through A5 3.3 and is triggered by malformed handshake or traffic packets that crash the device.

MitigationApply Cisco-provided software updates beyond version A5 3.3 when available. If no patch exists, consider network segmentation to limit exposure and implement rate limiting on SSL/TLS traffic as a temporary compensating control.

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
Ace Application Control Engine Module A1Plugin / extension
Affected:= 7a= 7b= 8.0= 8.0a
Ace Application Control Engine Module A3Plugin / extension
Affected:= 1.0= 2.0= 2.2= 2.3= 2.4= 2.5= 2.6= 2.7
Ace Application Control Engine Module A4Plugin / extension
Affected:= 1.0= 1.1= 2.0= 2.1a= 2.2= 2.3
Ace Application Control Engine Module A5Plugin / extension
Affected:= 1.0= 1.1= 1.2= 2.0= 2.1= 2.1e= 3.0= 3.1a= 3.1b= 3.2= 3.3
Ace 4700 Series Application Control Engine ApplianceHardware / appliance
Affected:= a5\(1.0\)= a5\(1.1\)= a5\(1.2\)= a5\(2.0\)= a5\(2.1\)= a5\(2.1e\)= a5\(3.0\)= a5_base
Ace 4700 Series Application Control Engine Appliance A1Hardware / appliance
Affected:= 7= 7a= 7b= 8.0= 8.0a
Ace 4700 Series Application Control Engine Appliance A3Hardware / appliance
Affected:= 1.0= 2.0= 2.2= 2.3= 2.4= 2.5= 2.6= 2.7
Ace 4700 Series Application Control Engine Appliance A4Hardware / appliance
Affected:= 1.0= 1.1= 2.0= 2.1a= 2.2= 2.3

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
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 checks

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

  1. Identify the device model
    Run 'show version' or check the hardware label to confirm the device is a Cisco ACE30 Application Control Engine Module or ACE 4700 Series Appliance
    Affected if The device model is Cisco ACE30 or ACE 4700 Series
  2. Check the installed software version
    Run 'show version' and locate the software version string (for example, A5.x, A4.x, A3.x, or A1.x)
    Affected if The version matches any of the affected ranges: A1 (7a, 7b, 8.0, 8.0a), A3 (1.0, 2.0, 2.2-2.7), A4 (1.0, 1.1, 2.0-2.3), or A5 (1.0-3.3)
  3. Verify SSL/TLS termination is configured
    Run 'show running-config' or 'show ssl' to check if SSL termination, SSL proxy service, or any SSL/TLS-related policies are configured on the device
    Affected if SSL or TLS termination is enabled and processing SSL/TLS traffic
  4. Check for SSL service policies
    Run 'show ssl service detail' or review the SSL service configuration to confirm active SSL termination sessions are being processed
    Affected if SSL termination service is actively running and processing SSL/TLS connections

The device is affected if it is a Cisco ACE30 or ACE 4700 running software version A5 3.3 or earlier (A1, A3, A4, or A5 branches) and has SSL/TLS termination services enabled.

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-provided software updates beyond version A5 3.3 when available. If no patch exists, consider network segmentation to limit exposure and implement rate limiting on SSL/TLS traffic as a temporary compensating control.

Fix this in Ace Application Control Engine Module A1 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
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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-2016-6399 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