CVE-2016-6415 is an ikev1 information disclosure vulnerability in Cisco IOS, IOS XR, and IOS XE. CISA added it to the Known Exploited Vulnerabilities catalogue on 19 May 2023, which means attackers have used it in real attacks. contains an information disclosure vulnerability in the Internet Key Exchange version 1 (IKEv1) that could allow an attacker to retrieve memory contents.
What this vulnerability means in Cisco IOS, IOS XR, and IOS XE
CVE-2016-6415 is not a simple configuration mistake, it is an information disclosure flaw in IKEv1 that can expose memory contents from network infrastructure devices. That matters because memory disclosure can reveal sensitive runtime data that should never be observable outside the device boundary, especially on systems handling VPN negotiation and cryptographic state.
For operators, the practical issue is not only whether the bug exists in a code line, but whether the affected device is reachable in a way that lets IKEv1 traffic reach the vulnerable path. Cisco’s own advisory and the NIST National Vulnerability Database are the authoritative places to confirm product scope, while the CVE Program is the canonical identifier source for the record itself.
Why IKEv1 information disclosure is dangerous
IKEv1 is used to establish and maintain secure communications, so a memory disclosure issue in that control path can undermine trust in the device even if remote code execution is not part of the vulnerability. Exposed memory may contain fragments of session material, protocol state, or other operational data that helps an attacker understand the device and its current security posture.
On internet-facing edge devices, that kind of exposure is especially concerning because the attack surface is often public and repeated probing is cheap. A flaw that leaks memory from a routing or VPN platform can become an intelligence source for follow-on exploitation, especially when the device is also supporting other management or tunnelling functions.
How organisations assess exposure and prioritise response
Exposure checking should start with an accurate inventory of Cisco IOS, IOS XR, and IOS XE assets, then narrow to devices actually running IKEv1 in a reachable context. Internet exposure matters because externally reachable management or VPN services are easier to target, and vendor advisories should be checked alongside the KEV catalogue to confirm why the issue is treated as actively exploited.
When prioritising remediation, organisations should treat the KEV listing as a signal to move beyond routine backlog sequencing. The Vulnerability Management Guide is useful here because it frames the response around asset scope, KEV-based prioritisation, verification, and exception handling rather than around CVE labels alone.
Remediation, detection, and compromise review
Where patching is delayed, organisations should reduce exposure by constraining access to the vulnerable service, limiting who can reach the device, and applying compensating controls that reduce the number of observable attack paths. For a network infrastructure flaw, the priority is to shrink exposure while maintaining service continuity, not to assume the device is safe because it remains stable.
After remediation, teams should review for signs of pre-patch compromise or unusual activity around the device’s management and VPN functions. If memory disclosure was exploited, defenders should consider whether any credentials, session material, or related secrets could have been observed indirectly and whether further review of adjacent systems is warranted.
Risk and Threat Considerations
Information disclosure bugs on perimeter networking equipment are attractive because they can give attackers passive visibility without immediately breaking the device. In a VPN or routing context, that visibility can help an attacker map the environment, identify useful secrets or state, and shape later intrusion steps.
Failure mechanism: The vulnerable IKEv1 code path returns data from process memory that should have remained inaccessible, allowing an external requester to harvest runtime contents.
Impact: The disclosure can expose sensitive operational information, support follow-on exploitation, and increase the likelihood that adjacent credentials or session-related material are targeted next.
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, CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SC-7 — Boundary Protection | This flaw matters most where perimeter controls fail to restrict reachability to the vulnerable IKEv1 service. |
| RA-5 — Vulnerability Monitoring and Scanning | The term requires asset-level exposure confirmation and prioritised vulnerability tracking. | |
| SI-2 — Flaw Remediation | The vulnerability requires timely remediation and verification after fix deployment. | |
| Recommendation — Restrict exposure to the affected VPN path and segment the device behind boundary controls. Scan Cisco assets for the vulnerable condition and track remediation to closure. Apply vendor remediation promptly and verify the vulnerable condition is removed. | ||
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | Active exploitation and KEV placement make prioritised vulnerability management directly relevant. |
| CIS-12 — Network Infrastructure Management | Cisco IOS-family infrastructure and exposure of network services fall directly under infrastructure hardening. | |
| Recommendation — Prioritise this KEV-listed issue in your vulnerability management workflow. Harden and inventory network devices that expose the vulnerable IKEv1 service. | ||
| NIST CSF 2.0 | PR.PS-01 — Configuration Management | Mitigation depends on securely managing the device configuration and exposure of the service. |
| DE.CM-09 — Network Monitoring | Detection of suspicious access to perimeter devices depends on monitoring network activity and service exposure. | |
| Recommendation — Manage device configuration so the vulnerable service is not unnecessarily exposed. Monitor network-facing device activity for unusual probing of the affected service. | ||
Practitioner Guidance
Why practitioners should care: Treat this class of flaw as an exposure problem on security infrastructure, not just a software defect. The right response is to confirm whether the device is exposed, whether IKEv1 is actually needed, and whether the asset is already covered by prioritised remediation because it appears in KEV.
What to watch for: Focus on edge devices with broad network reach, long maintenance intervals, or weak asset ownership, because those are the systems most likely to stay exposed after disclosure. If a device cannot be patched immediately, the temporary control objective is to reduce reachability and keep the exposure window as small as possible.
Related resources from NHI Mgmt Group
- What are the signs that Cisco IOS XE systems may be vulnerable to CVE-2023-20198?
- CVE-2023-20109 (Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write)
- CVE-2017-12319 (Cisco IOS XE Software Ethernet Virtual Private Network Border Gateway Protocol Denial-of-Service)
- CVE-2025-20352 (Cisco IOS and IOS XE Software SNMP Denial of Service and Remote Code Execution)