CVE-2016-6366

CVE-2016-6366 is a high-severity vulnerability in Cisco Pix Firewall Software with a CVSS 3.x base score of 8.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2022-05-24). The underlying weakness is classified as CWE-120.

Key facts

• Severity: High (CVSS 3.x base score 8.8)
• CVSS v2: 8.5
• EPSS exploit prediction: 88% (100th percentile)
• Actively exploited: Yes — listed in CISA KEV (added 2022-05-24)
• EU (EUVD) id: EUVD-2016-7289
• EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2022-05-24)
• Weakness: CWE-120
• Affected product: Cisco Pix Firewall Software
• Published: 2016-08-18
• Last modified: 2026-06-17

Description

Buffer overflow in Cisco Adaptive Security Appliance (ASA) Software through 9.4.2.3 on ASA 5500, ASA 5500-X, ASA Services Module, ASA 1000V, ASAv, Firepower 9300 ASA Security Module, PIX, and FWSM devices allows remote authenticated users to execute arbitrary code via crafted IPv4 SNMP packets, aka Bug ID CSCva92151 or EXTRABACON.

Frequently asked questions

What is CVE-2016-6366?

Buffer overflow in Cisco Adaptive Security Appliance (ASA) Software through 9.4.2.3 on ASA 5500, ASA 5500-X, ASA Services Module, ASA 1000V, ASAv, Firepower 9300 ASA Security Module, PIX, and FWSM devices allows remote authenticated users to execute arbitrary code via crafted IPv4 SNMP packets, aka Bug ID CSCva92151 or EXTRABACON.

How severe is CVE-2016-6366?

CVE-2016-6366 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2016-6366 being actively exploited?

Yes. CVE-2016-6366 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2022-05-24, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2016-6366?

CVE-2016-6366 primarily affects Cisco Pix Firewall Software. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-6366?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2016-6366 have an EU (EUVD) identifier?

Yes. CVE-2016-6366 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2016-7289. It is also flagged as exploited in the EUVD (since 2022-05-24).

When was CVE-2016-6366 published?

CVE-2016-6366 was published on 2016-08-18 and last updated on 2026-06-17.

References

• http://blogs.cisco.com/security/shadow-brokers
• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160817-asa-snmp
• http://tools.cisco.com/security/center/viewErp.x?alertId=ERP-56516
• http://www.securityfocus.com/bid/92521
• http://www.securitytracker.com/id/1036637
• https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/40258.zip
• https://www.exploit-db.com/exploits/40258/
• https://zerosum0x0.blogspot.com/2016/09/reverse-engineering-cisco-asa-for.html
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-6366

Affected products (4)

• cpe:2.3:o:cisco:pix_firewall_software:-:*:*:*:*:*:*:*
• cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
• cpe:2.3:o:cisco:asa_1000v_cloud_firewall_software:8.7.1:*:*:*:*:*:*:*
• cpe:2.3:o:cisco:asa_1000v_cloud_firewall_software:8.7.1.1:*:*:*:*:*:*:*

More vulnerabilities in Cisco Pix Firewall Software

• CVE-2007-0960 — Critical (CVSS 9.0): Unspecified vulnerability in Cisco PIX 500 and ASA 5500 Series Security Appliances 7.2.2, when configured to use the…
• CVE-2007-0961 — High (CVSS 7.8): Cisco PIX 500 and ASA 5500 Series Security Appliances 6.x before 6.3(5.115), 7.0 before 7.0(5.2), and 7.1 before…
• CVE-2007-0959 — High (CVSS 7.8): Cisco PIX 500 and ASA 5500 Series Security Appliances 7.2.2, when configured to inspect certain TCP-based protocols,…
• CVE-2007-0962 — High (CVSS 7.8): Cisco PIX 500 and ASA 5500 Series Security Appliances 7.0 before 7.0(4.14) and 7.1 before 7.1(2.1), and the FWSM 2.x…
• CVE-2003-1003 — High (CVSS 7.8): Cisco PIX firewall 5.x.x, and 6.3.1 and earlier, allows remote attackers to cause a denial of service (crash and…
• CVE-2006-0515 — High (CVSS 7.5): Cisco PIX/ASA 7.1.x before 7.1(2) and 7.0.x before 7.0(5), PIX 6.3.x before 6.3.5(112), and FWSM 2.3.x before 2.3(4)…

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