CVE-2025-20162 in IOS XE Software
Summary
by MITRE • 05/07/2025
A vulnerability in the DHCP snooping security feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a full interface queue wedge, which could result in a denial of service (DoS) condition.
This vulnerability is due to improper handling of DHCP request packets. An attacker could exploit this vulnerability by sending DHCP request packets to an affected device. A successful exploit could allow the attacker to cause packets to wedge in the queue, creating a DoS condition for downstream devices of the affected system and requiring that the system restart to drain the queue.
Note: This vulnerability can be exploited with either unicast or broadcast DHCP packets on a VLAN that does not have DHCP snooping enabled.
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Analysis
by VulDB Data Team • 07/11/2025
This vulnerability exists within the DHCP snooping security feature of Cisco IOS XE Software, representing a critical denial of service weakness that can be exploited remotely without authentication. The flaw stems from inadequate processing of DHCP request packets, specifically when these packets are received on VLANs where DHCP snooping is not enabled. The vulnerability manifests as a queue wedge condition that affects the full interface queue of the affected device, creating a cascading denial of service that impacts all downstream network devices connected to that interface. The security implications are particularly concerning because the attack can be executed through either unicast or broadcast DHCP packets, providing multiple exploitation vectors for potential attackers. This weakness directly violates the fundamental security principle of maintaining network availability and can severely disrupt business operations by cutting off network connectivity for all devices relying on the affected interface.
The technical root cause of this vulnerability lies in the improper handling of DHCP request packets within the software's packet processing logic. When DHCP requests are received on VLANs without DHCP snooping enabled, the system fails to properly manage the packet flow through the interface queue, causing packets to accumulate and wedge in the queue structure. This queue wedge condition prevents normal packet processing and effectively blocks network communication for downstream devices. The vulnerability is classified under CWE-129 as an improper input validation issue, specifically related to insufficient handling of network packets in security contexts. From an operational perspective, the impact extends beyond simple connectivity loss as the affected system requires a complete restart to clear the wedged queue, resulting in extended downtime and potential service disruption for all network users dependent on that interface. The attack vector is particularly dangerous because it requires no authentication credentials and can be executed from remote locations, making it an attractive target for malicious actors seeking to disrupt network services.
The operational impact of this vulnerability creates significant risk for organizations relying on Cisco IOS XE Software for network infrastructure management. Network administrators face the challenge of maintaining service availability while dealing with the requirement for system restarts to resolve the queue wedge condition. This vulnerability can be exploited by attackers to perform sustained denial of service attacks, potentially causing extended network outages that affect critical business operations. The attack can be particularly damaging in environments where network availability is paramount, such as financial institutions, healthcare organizations, or telecommunications providers. From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, where attackers leverage software weaknesses to create persistent network disruptions. The exploitability characteristics make this vulnerability particularly dangerous as it can be executed through standard DHCP traffic patterns, making it difficult to distinguish from legitimate network operations and complicating detection efforts. Organizations must consider implementing network segmentation and monitoring solutions to detect unusual DHCP traffic patterns that could indicate exploitation attempts.
Mitigation strategies for this vulnerability should include immediate deployment of Cisco's security patches and updates as released through their official advisory channels. Network administrators should consider disabling DHCP snooping on VLANs where it is not required, particularly in environments where the risk of exploitation is high. Implementing network monitoring solutions that can detect unusual DHCP packet patterns and queue behavior can provide early warning of potential exploitation attempts. Organizations should also establish robust incident response procedures that include immediate system restart protocols when queue wedge conditions are detected. The implementation of network access control lists and firewall rules to limit DHCP traffic on affected interfaces can provide additional protection layers. Regular security assessments and vulnerability scanning should be conducted to identify other potential weaknesses in the network infrastructure that could be exploited in conjunction with this vulnerability. Additionally, network teams should maintain detailed documentation of all network configurations and regularly review DHCP snooping settings to ensure proper enforcement across all network segments. The vulnerability underscores the importance of maintaining current security patches and implementing defense-in-depth strategies to protect against both known and emerging threats in network infrastructure components.