CVE-2017-5632 in RT-N56U
Summary
by MITRE
An issue was discovered on the ASUS RT-N56U Wireless Router with Firmware 3.0.0.4.374_979. When executing an "nmap -O" command that specifies an IP address of an affected device, one can crash the device's WAN connection, causing disconnection from the Internet, a Denial of Service (DoS). The attack is only possible from within the local area network.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/17/2026
The CVE-2017-5632 vulnerability represents a significant denial of service weakness in ASUS RT-N56U wireless routers running specific firmware versions. This vulnerability manifests through a carefully crafted network scan that exploits a flaw in the router's handling of certain network packets, specifically those generated by nmap's operating system detection feature. The issue is particularly concerning because it allows local network attackers to disrupt internet connectivity for the affected device, effectively creating a denial of service condition that can impact network operations and user productivity.
The technical flaw underlying this vulnerability stems from inadequate input validation within the router's network processing stack. When the affected ASUS router receives malformed or specially crafted packets during network discovery operations, particularly those generated by nmap's -O flag for operating system detection, the device fails to properly handle these packets and subsequently crashes its WAN connection. This represents a classic buffer overflow or input validation error that falls under the CWE-121 category of buffer overflow conditions, where insufficient bounds checking allows malicious input to corrupt memory and cause system instability.
The operational impact of this vulnerability extends beyond simple connectivity disruption as it can severely impact network availability for organizations or households relying on the affected router. The DoS condition specifically targets the WAN connection, meaning that any services dependent on internet connectivity would become unavailable until manual intervention restores the connection. This vulnerability is particularly dangerous in environments where network uptime is critical, as it can be exploited by malicious actors within the local network to disrupt services without requiring external access. The attack vector being limited to local network access means that while the scope is constrained, it still represents a significant internal threat vector that can be leveraged by insider threats or compromised local network devices.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, where adversaries manipulate network infrastructure to disrupt services. The local network requirement for exploitation means that traditional perimeter security measures may not prevent this attack, highlighting the need for internal network segmentation and monitoring. Organizations should prioritize firmware updates to address this vulnerability, as ASUS has released patches for affected firmware versions. Additionally, implementing network access controls, monitoring for unusual network scanning activity, and maintaining up-to-date network device inventories can help detect and prevent exploitation attempts. The vulnerability also underscores the importance of network device security hardening practices and regular security assessments to identify similar weaknesses in network infrastructure components that may not be immediately apparent through standard security scanning procedures.