CVE-2016-6367 is a CLI remote code execution vulnerability in Cisco Adaptive Security Appliance (ASA). CISA added it to the Known Exploited Vulnerabilities catalogue on 24 May 2022, which means attackers have used it in real attacks. Organisations running the affected product should apply the vendor fix or mitigation as a priority.
What this vulnerability means in practice
CVE-2016-6367 is dangerous because it affects the command interface of a security appliance, which sits close to the trust boundary for remote administration. If an attacker can reach and exploit that interface, the result can be full device compromise rather than a narrow application bug, which is why KEV-listed appliance flaws demand fast attention.
For the vulnerability record itself, use the authoritative entries in the CVE Program and NIST National Vulnerability Database instead of relying on secondary summaries for technical detail.
How organisations assess exposure
The first question is whether any Cisco ASA instances still exist, where they are exposed, and whether the management path can be reached from untrusted networks. That means pairing asset inventory with internet-facing discovery, device ownership, and review of vendor advisories so teams can identify the exact appliances that need attention.
When vulnerability management is mature, KEV status changes prioritisation because it tells defenders the flaw is not theoretical. NHIMG’s Vulnerability Management Guide is a useful companion for turning exposure data into remediation priority, while the vendor advisory remains the source of truth for fix and mitigation details.
Remote access design also matters because appliance management surfaces are often reachable through VPNs, portals, or other remote administration paths. VPN Security Guide and Remote Access Identity Guide help readers think about how exposure expands when administrative entry points are broadly reachable.
Remediation and compensating controls
The preferred response is to apply the vendor fix or mitigation as soon as operationally possible, then remove any temporary exposure reduction once the appliance is safe again. Where patching cannot happen immediately, defenders should reduce reachability, tighten administrative access, and treat the device as a high-value target until the exposure window closes.
A practical way to think about this is to shrink both the attack surface and the number of people or systems that can touch the ASA. The same control logic appears in Secure Coding Guide at the design level and in Network Ports and Protocols Security Guide at the exposure level: limit unnecessary access paths, reduce trusted ingress, and avoid leaving sensitive management interfaces broadly available.
Detection and post-patch review
Exploitation of a CLI RCE often leaves only partial evidence, so defenders should review logs, command history, configuration changes, and any unusual outbound activity around the exposure window. Patch installation alone is not enough if the appliance was already compromised before remediation.
After patching, organisations should look for signs that the device was used as a foothold for lateral movement, credential capture, or configuration tampering. The broader compromise pattern is well illustrated by NHIMG’s State of NHI & AI Agent Breach Report and Salt Typhoon telecom intrusions 2025, which show how initial access can turn into persistence and broader environment compromise.
Risk and Threat Considerations
Appliance CLI RCE is high impact because a successful exploit can give an attacker direct control of a perimeter or remote-access device. That combination makes the flaw attractive for initial access, persistence, and follow-on movement, especially when the appliance is exposed to the internet or administered from weakly controlled networks.
Failure mechanism: The attacker abuses command execution in a management plane that was trusted to perform administrative actions, then uses that control to change configuration, intercept traffic, or establish a durable foothold.
Impact: Compromise can extend beyond the appliance itself and expose adjacent systems, credentials, and internal pathways that depend on it for trust or connectivity.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-2 — Flaw Remediation | CVE remediation and KEV prioritization rely on flaw remediation for the affected ASA. |
| AU-6 — Audit Record Review, Analysis, and Reporting | Post-exploit review depends on reviewing logs and events for compromise indicators. | |
| AC-17 — Remote Access | The vulnerability is dangerous on a remotely administered security appliance, where access paths must be constrained. | |
| Recommendation — Prioritize and remediate the ASA flaw immediately, then verify the fix across all exposed instances. Review appliance and perimeter logs for signs of exploitation, drift, and suspicious administrative activity. Restrict remote administrative access to the ASA to the smallest necessary set of trusted sources. | ||
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | KEV status and exposed appliances make continuous vulnerability tracking central to this CVE. |
| CIS-12 — Network Infrastructure Management | ASA is a network security appliance, so hardening its management surface is part of infrastructure control. | |
| Recommendation — Track exposed ASA instances and accelerate remediation for any device listed in KEV. Harden and segment network appliance management paths to reduce exploitable exposure. | ||
Practitioner Guidance
Why practitioners should care: KEV listing means this is not just a catalog entry, it is a known exploitation path with real operational consequences. Treat the ASA as an urgent remediation item, not a routine maintenance task, and verify that the device is actually reachable only through the smallest necessary set of administrative paths.
What to watch for: Focus on unexpected configuration drift, unusual admin logins, new local accounts or keys, and outbound connections that do not fit the appliance’s normal role. If any of those appear, assume the device may need compromise review even after remediation is complete.
Vulnerability Management GuideRelated resources from NHI Mgmt Group
- CVE-2026-20349 (Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection)
- CVE-2025-20333 (Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow)
- CVE-2025-20362 (Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Missing Authorization)
- CVE-2014-2120 (Cisco Adaptive Security Appliance (ASA) Cross-Site Scripting (XSS))
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Reviewed and updated by the NHIMG editorial team on October 17, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org