CVE-2025-20162 Overview
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.
Notably, this vulnerability can be exploited with either unicast or broadcast DHCP packets on a VLAN that does not have DHCP snooping enabled, making it particularly dangerous in environments where DHCP snooping is not comprehensively deployed across all VLANs.
Critical Impact
Remote attackers can cause a complete denial of service on Cisco IOS XE devices by sending malicious DHCP packets, affecting all downstream network devices and requiring a system restart to recover.
Affected Products
- Cisco IOS XE versions 16.11.x through 16.12.x
- Cisco IOS XE versions 17.1.x through 17.15.x
- Cisco IOS XE Software with DHCP snooping feature
Discovery Timeline
- May 7, 2025 - CVE-2025-20162 published to NVD
- July 11, 2025 - Last updated in NVD database
Technical Details for CVE-2025-20162
Vulnerability Analysis
This vulnerability resides within the DHCP snooping security feature implementation in Cisco IOS XE Software. The core issue stems from improper handling of DHCP request packets, classified under CWE-400 (Uncontrolled Resource Consumption). When the affected device processes specially crafted DHCP requests, the packets become wedged in the interface queue, leading to resource exhaustion and a complete denial of service condition.
The vulnerability is particularly concerning because it requires no authentication or user interaction to exploit. An attacker with network access can trigger the condition remotely, and the impact extends beyond the targeted device to affect all downstream network infrastructure. The scope of impact is characterized as "changed" in the CVSS assessment, meaning systems beyond the vulnerable component are affected.
Root Cause
The root cause is improper handling of DHCP request packets within the DHCP snooping feature of Cisco IOS XE Software. When processing these packets, the system fails to properly manage queue resources, allowing malicious packets to accumulate and wedge in the interface queue. This resource exhaustion condition prevents normal packet processing and cannot be cleared without a full system restart.
The vulnerability is exacerbated by the fact that it can be triggered on VLANs where DHCP snooping is not enabled, meaning that even partial deployment of the DHCP snooping feature creates exposure to this attack vector.
Attack Vector
The attack can be executed remotely over the network without requiring any privileges or user interaction. An attacker needs only network access to send DHCP request packets—either unicast or broadcast—to an affected Cisco IOS XE device. The attack targets VLANs that do not have DHCP snooping enabled, which may include infrastructure VLANs or segments where administrators have not yet deployed comprehensive DHCP security controls.
The exploitation mechanism involves sending crafted DHCP request packets that trigger the improper handling condition. Once packets begin wedging in the queue, the condition persists and worsens, eventually causing a complete interface queue wedge that blocks all traffic processing for downstream devices.
Detection Methods for CVE-2025-20162
Indicators of Compromise
- Unusual DHCP traffic patterns including high volumes of DHCP request packets
- Interface queue utilization approaching or reaching capacity limits
- Downstream device connectivity failures or network outages
- System logs showing DHCP-related processing errors or queue warnings
Detection Strategies
- Monitor network traffic for abnormal DHCP packet volumes using network monitoring tools
- Configure SNMP traps or syslog alerts for interface queue threshold violations
- Implement NetFlow or similar flow analysis to detect DHCP traffic anomalies
- Review Cisco IOS XE device logs for DHCP snooping related errors or warnings
Monitoring Recommendations
- Enable interface queue monitoring and set alerting thresholds at 70-80% utilization
- Deploy network behavior analysis tools to baseline normal DHCP traffic patterns
- Configure logging for all DHCP-related events on Cisco IOS XE devices
- Implement real-time monitoring for sudden network connectivity degradation affecting downstream devices
How to Mitigate CVE-2025-20162
Immediate Actions Required
- Review Cisco's security advisory and determine if your IOS XE version is affected
- Identify all VLANs where DHCP snooping is not currently enabled
- Prioritize patching of devices in critical network segments
- Consider enabling DHCP snooping on all VLANs as an interim measure
- Prepare system restart procedures in case of active exploitation
Patch Information
Cisco has released security patches addressing this vulnerability. Organizations should consult the Cisco Security Advisory for specific fixed software versions and upgrade guidance. Given the wide range of affected versions (16.11.x through 17.15.x), administrators should verify their current version and identify the appropriate upgrade path.
The fixed versions address the improper DHCP packet handling that allows queue wedging to occur. After patching, devices will properly process or discard malformed DHCP requests without allowing resource exhaustion.
Workarounds
- Enable DHCP snooping on all VLANs to ensure consistent protection across the network
- Implement access control lists (ACLs) to restrict DHCP traffic to authorized DHCP servers
- Deploy rate limiting for DHCP traffic at network ingress points
- Segment critical infrastructure to isolate potential impact from exploitation
- Monitor interface queues and configure automated alerts for anomalous utilization
# Enable DHCP snooping globally and on all VLANs
ip dhcp snooping
ip dhcp snooping vlan 1-4094
# Configure trusted interfaces for legitimate DHCP servers
interface GigabitEthernet0/0/1
ip dhcp snooping trust
# Implement rate limiting for DHCP traffic
interface GigabitEthernet0/0/2
ip dhcp snooping limit rate 100
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
