What is CVE-2016-6399?

CVE-2016-6399 is a high-severity vulnerability in Cisco Ace 4700 Series Application Control Engine Appliance, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2016-09-12.

How severe is CVE-2016-6399?

High severity. CVSS v3 base score is 7.5 out of 10.

Improper input validation in Cisco Ace 4700 Series Application Control Engine Appliance

CVE-2016-6399

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2016-09-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.019 (79.4th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 79th percentile — 79.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.019 · newest: 0.019 · change: 0.000

Affected products

Cisco Ace 4700 Series Application Control Engine Appliance — versions a5_base, a5(2.0), a5\(3.0\)
Cisco Ace 4700 Series Application Control Engine Appliance A1 — versions 7, 7a, 7b
Cisco Ace 4700 Series Application Control Engine Appliance A3 — versions 1.0, 2.0, 2.2
Cisco Ace 4700 Series Application Control Engine Appliance A4 — versions 1.0, 1.1, 2.0
Cisco Ace 4700 Series Application Control Engine Appliance A5 — versions 3.1a, 3.1b, 3.2
Cisco Ace Application Control Engine Module A1 — versions 7a, 7b, 8.0
Cisco Ace Application Control Engine Module A3 — versions 1.0, 2.0, 2.2
Cisco Ace Application Control Engine Module A4 — versions 1.0, 1.1, 2.0
Cisco Ace Application Control Engine Module A5 — versions 1.0, 1.1, 1.2

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160908… (vendor-advisory, Vendor Advisory)
www.securityfocus.com/bid/92867 (vdb-entry)
www.securitytracker.com/id/1036748 (vdb-entry)

Frequently asked questions

What is CVE-2016-6399?: CVE-2016-6399 is a high-severity vulnerability in Cisco Ace 4700 Series Application Control Engine Appliance, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2016-09-12.
How severe is CVE-2016-6399?: High severity. CVSS v3 base score is 7.5 out of 10.