How severe is CVE-2016-6399?

CVE-2016-6399 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2016-6399 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-6399?

CVE-2016-6399 primarily affects Cisco Ace Application Control Engine Module A1. In total, 60 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-6399?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2016-6399 published?

CVE-2016-6399 was published on 2016-09-12 and last updated on 2026-06-17.

CVE-2016-6399

CVE-2016-6399 is a high-severity vulnerability in Cisco Ace Application Control Engine Module A1 with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Cisco Ace Application Control Engine Module A1
Published: 2016-09-12
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2016-6399?: CVE-2016-6399 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2016-6399 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-6399?: CVE-2016-6399 primarily affects Cisco Ace Application Control Engine Module A1. In total, 60 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-6399?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2016-6399 published?: CVE-2016-6399 was published on 2016-09-12 and last updated on 2026-06-17.

References

Affected products (60)

cpe:2.3:a:cisco:ace_application_control_engine_module_a1:7a:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a1:7b:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a1:8.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a1:8.0a:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:1.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.4:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.5:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.6:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a3:2.7:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:1.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:1.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:2.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:2.1a:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:2.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a4:2.3:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:1.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:1.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:1.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:2.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:2.1:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:2.1e:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:3.0:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:3.1a:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:3.1b:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:3.2:*:*:*:*:*:*:*
cpe:2.3:a:cisco:ace_application_control_engine_module_a5:3.3:*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(1.0\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(1.1\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(1.2\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(2.0\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(2.1\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(2.1e\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5\(3.0\):*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance:a5_base:*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance_a1:7:*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance_a1:7a:*:*:*:*:*:*:*
cpe:2.3:h:cisco:ace_4700_series_application_control_engine_appliance_a1:7b:*:*:*:*:*:*:*

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