CVE-2016-10227 in USG50
Summary
by MITRE
Zyxel USG50 Security Appliance and NWA3560-N Access Point allow remote attackers to cause a denial of service (CPU consumption) via a flood of ICMPv4 Port Unreachable packets.
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Analysis
by VulDB Data Team • 02/21/2017
The vulnerability identified as CVE-2016-10227 affects Zyxel USG50 Security Appliances and NWA3560-N Access Points, representing a significant denial of service weakness that can be exploited remotely by attackers. This flaw resides within the network security device's handling of ICMPv4 Port Unreachable packets, which are standard network protocol messages used to indicate when a destination port is unreachable. The vulnerability specifically manifests when these devices receive a high volume of such packets, leading to excessive CPU utilization and ultimately causing a denial of service condition that disrupts legitimate network operations.
The technical implementation of this vulnerability stems from inadequate input validation and resource management within the affected Zyxel devices. When processing ICMPv4 Port Unreachable packets, the security appliances fail to properly rate limit or filter these messages, allowing an attacker to flood the device with a sustained stream of such packets. This results in the device's CPU resources becoming consumed at elevated levels, often reaching 100% utilization, which prevents the appliance from processing legitimate network traffic and maintaining its security functions. The flaw operates at the network protocol level, making it particularly dangerous as it can be exploited without requiring authentication or specialized access privileges.
From an operational impact perspective, this vulnerability creates substantial risk for organizations relying on Zyxel security appliances for network protection. The denial of service condition can render critical network infrastructure inaccessible, potentially disrupting business operations and compromising network security posture. Network administrators may experience significant downtime while attempting to restore service, as the affected devices become unresponsive to legitimate traffic and management access. The vulnerability particularly affects enterprise networks where these appliances serve as primary security gateways, potentially exposing the entire network to additional attack vectors during the service disruption period.
The mitigation strategies for this vulnerability should encompass both immediate defensive measures and long-term architectural improvements. Organizations should implement rate limiting and access control lists to restrict the volume of ICMPv4 Port Unreachable packets that can traverse the affected devices. Network segmentation and firewall rules can help isolate these appliances from potentially malicious traffic sources while monitoring for unusual packet patterns. Additionally, applying vendor-provided security patches and firmware updates represents the most effective long-term solution, as these updates typically include enhanced packet filtering mechanisms and improved resource management. The vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption," and corresponds to ATT&CK technique T1499.004, "Endpoint Denial of Service," demonstrating how network infrastructure devices can be targeted to create service disruptions through resource exhaustion attacks.