CVE-2017-6627 in IOS
Summary
by MITRE
A vulnerability in the UDP processing code of Cisco IOS 15.1, 15.2, and 15.4 and IOS XE 3.14 through 3.18 could allow an unauthenticated, remote attacker to cause the input queue of an affected system to hold UDP packets, causing an interface queue wedge and a denial of service (DoS) condition. The vulnerability is due to Cisco IOS Software application changes that create UDP sockets and leave the sockets idle without closing them. An attacker could exploit this vulnerability by sending UDP packets with a destination port of 0 to an affected device. A successful exploit could allow the attacker to cause UDP packets to be held in the input interfaces queue, resulting in a DoS condition. The input interface queue will stop holding UDP packets when it receives 250 packets. Cisco Bug IDs: CSCup10024, CSCva55744, CSCva95506.
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Analysis
by VulDB Data Team • 02/05/2025
The vulnerability described in CVE-2017-6627 represents a critical denial of service weakness within Cisco IOS and IOS XE software implementations that affects versions 15.1, 15.2, and 15.4 along with IOS XE versions 3.14 through 3.18. This flaw operates at the network protocol level by exploiting improper handling of UDP packet processing within the software stack. The vulnerability stems from a design flaw where UDP sockets are created and maintained in an idle state without proper resource cleanup, creating a persistent condition that can be exploited by remote attackers. The specific technical mechanism involves the software's failure to properly close UDP sockets after their initial creation, leading to resource exhaustion and queue saturation. This issue falls under the CWE-400 category of Uncontrolled Resource Consumption, which is a fundamental weakness in resource management that can lead to system instability and service disruption.
The operational impact of this vulnerability manifests as a complete denial of service condition on affected Cisco devices, where network interfaces become unable to process incoming UDP traffic effectively. Attackers can exploit this weakness by sending UDP packets with destination port zero to the target system, which triggers the problematic code path that leaves sockets idle and unmanaged. The system's input queue becomes saturated with UDP packets, creating a queue wedge condition that prevents normal network operations from functioning properly. The vulnerability has a specific saturation point where the input interface queue stops accepting additional UDP packets after receiving 250 packets, which creates a predictable exploitation pattern. This behavior directly aligns with the ATT&CK technique T1499.004 for Network Denial of Service, where attackers leverage protocol implementation weaknesses to disrupt network services. The DoS condition effectively renders network interfaces non-functional, potentially causing widespread service interruption across the affected network infrastructure.
Mitigation strategies for CVE-2017-6627 require immediate implementation of software patches and updates provided by Cisco to address the root cause of the UDP socket management issue. Network administrators should prioritize applying the relevant security advisories and firmware updates that correct the resource cleanup mechanism for UDP sockets. In addition to patching, network segmentation and access control measures should be implemented to limit exposure to potential attackers, particularly by blocking UDP traffic with destination port zero at network boundaries. The implementation of rate limiting and packet filtering rules can help reduce the impact of exploitation attempts by limiting the volume of UDP packets that can be processed by affected interfaces. Monitoring and alerting systems should be configured to detect unusual patterns in interface queue behavior and packet processing, enabling rapid response to potential exploitation attempts. Organizations should also consider implementing network access control lists that specifically block UDP packets destined for port zero to prevent exploitation of this specific vulnerability. The remediation process must include comprehensive testing of patched systems to ensure that the fix does not introduce compatibility issues with existing network services while maintaining the security posture against this particular denial of service threat.