What Is CVE-2017-6627 (Cisco IOS Software and Cisco IOS XE Software UDP Packet Processing Denial-of-Service)?

By NHI Mgmt Group Updated October 17, 2026 Domain: Threats, Abuse & Incident Response

CVE-2017-6627 is an UDP packet processing denial-of-service vulnerability in Cisco IOS and IOS XE Software. CISA added it to the Known Exploited Vulnerabilities catalogue on 3 March 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 class means

This CVE belongs to a class of denial-of-service flaws in packet-processing logic. In practical terms, that means ordinary network traffic can trigger a failure path in the device’s forwarding or control-plane handling, turning an exposed router or switch into a service outage instead of a stable traffic path.

That is why packet-processing DoS issues are dangerous in infrastructure software: they can interrupt routing, management access, adjacent services, and downstream connectivity without needing code execution. For internet-facing or edge devices, the blast radius can extend well beyond the affected box because it often sits on a critical path for many users or sites.

How organisations check exposure

Exposure starts with asset inventory, because teams need to know exactly where Cisco IOS and IOS XE are deployed and which systems are reachable from untrusted networks. They should then compare those assets against the vendor advisory and the NIST National Vulnerability Database entry for authoritative vulnerability details, while also checking whether the affected devices are exposed at network boundaries.

Prioritisation should account for where the device sits, not just whether it exists. A vulnerable router used for campus, branch, data centre, or provider edge traffic is materially more urgent than a lab system with no external reachability, and organisations should correlate that with the CVE Program record and the CISA KEV listing referenced in the primary definition.

Remediation and compensating controls

Where a fix is available, the priority is to apply the vendor remediation promptly because KEV-listed exploitation means the issue is not theoretical. If patching must be delayed, reduce exposure by limiting who can reach the management and data planes, segmenting the device, and constraining traffic paths that could trigger the flaw.

Compensating controls matter most when the device cannot be taken out of service quickly. Rate limiting, ACL tightening, and upstream filtering can help reduce abuse opportunities, but they are not substitutes for a permanent fix when the vulnerable packet path remains reachable.

Detection and post-incident review

Detection should look for abnormal packet rates, repeated malformed traffic, device instability, interface resets, process crashes, or unexplained routing interruptions. Because denial-of-service events are often noisy rather than stealthy, telemetry from the network, the device itself, and upstream protection services should be reviewed together.

After patching or recovery, organisations should review whether the outage was purely a crash or whether it masked follow-on compromise, configuration changes, or persistence attempts. For this type of CVE, the main identity impact is usually indirect, but if administrators used emergency access during the event, any exposed credentials, sessions, or privileged access paths should be reviewed and rotated as needed.

Risk and Threat Considerations

Exploitability matters because infrastructure devices are often trusted, highly available, and difficult to isolate. An attacker who can trigger denial of service on a core router or edge device can create immediate business disruption, and in some environments the same failure can also be used as a diversion for other activity.

Failure mechanism: Malicious or malformed UDP traffic exercises a vulnerable packet-processing path until the device degrades, resets, or stops forwarding traffic reliably.

Impact: The result can be service outage, routing disruption, management-plane instability, and loss of availability for dependent systems and users.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

NIST CSF 2.0, 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 CSF 2.0	PR.PS-01 — Configuration Management	CVE remediation depends on secure device configuration and change control.
	PR.PS-04 — Supply Chain Risk Management	The subject requires reliance on vendor advisories and authoritative patch guidance.
	DE.CM-01 — Networks and Network Services Are Monitored to Find Potentially Adverse Events	Packet-processing DoS needs monitoring for abnormal traffic and service disruption.
Recommendation — Apply configuration management to deploy the vendor fix and reduce exposed attack paths. Track vendor advisories and approved remediation channels before changing production devices. Monitor network and device telemetry for traffic spikes, crashes, and routing instability.
NIST SP 800-53 Rev 5	SI-2 — Flaw Remediation	This CVE is a flaw-remediation problem requiring prompt patching or mitigation.
	SC-5 — Denial of Service Protection	The vulnerability is a denial-of-service condition against a network device.
	AU-6 — Audit Record Review, Analysis, and Reporting	Post-incident review needs logs and telemetry to confirm outage cause and scope.
Recommendation — Remediate the Cisco flaw promptly and verify the device no longer exposes the vulnerable path. Use denial-of-service protections to limit packet floods and traffic patterns that can exhaust the device. Review logs and event data to confirm whether the outage was isolated or accompanied by other suspicious activity.
CIS Controls v8	CIS-12 — Network Infrastructure Management	Cisco IOS and IOS XE are network infrastructure assets requiring inventory and secure operation.
	CIS-7 — Continuous Vulnerability Management	The term is a known exploited vulnerability that requires prioritised remediation.
Recommendation — Inventory, harden, and maintain network infrastructure devices before they become outage points. Prioritise the KEV-listed Cisco vulnerability in your remediation queue and validate closure.

Practitioner Guidance

Why practitioners should care: Treat KEV-listed network-device DoS flaws as operational incidents waiting to happen, not as low-severity hygiene items. For edge and backbone equipment, the security question is often uptime, because a single vulnerable device can affect many downstream services at once.

What to watch for: If the vulnerable device is exposed to broad network reachability or sits on a critical traffic path, it deserves expedited remediation, temporary exposure reduction, and close post-change verification. That combination usually matters more than the nominal severity label alone.

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NHIMG Editorial Note
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

CVE-2017-6627 (Cisco IOS Software and Cisco IOS XE Software UDP Packet Processing Denial-of-Service)