CVE-2017-11420 in RT-AC68P
Summary
by MITRE
Stack-based buffer overflow in ASUS_Discovery.c in networkmap in Asuswrt-Merlin firmware for ASUS devices and ASUS firmware for ASUS RT-AC5300, RT_AC1900P, RT-AC68U, RT-AC68P, RT-AC88U, RT-AC66U, RT-AC66U_B1, RT-AC58U, RT-AC56U, RT-AC55U, RT-AC52U, RT-AC51U, RT-N18U, RT-N66U, RT-N56U, RT-AC3200, RT-AC3100, RT_AC1200GU, RT_AC1200G, RT-AC1200, RT-AC53, RT-N12HP, RT-N12HP_B1, RT-N12D1, RT-N12+, RT_N12+_PRO, RT-N16, and RT-N300 devices allows remote attackers to execute arbitrary code via long device information that is mishandled during a strcat to a device list.
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Analysis
by VulDB Data Team • 10/27/2019
The vulnerability identified as CVE-2017-11420 represents a critical stack-based buffer overflow in the ASUS_Discovery.c component of the networkmap functionality within Asuswrt-Merlin firmware and various ASUS router models. This flaw exists in the handling of device information during network discovery operations, specifically when the strcat function processes incoming device data. The vulnerability affects a wide range of ASUS devices including the RT-AC5300, RT-AC1900P, RT-AC68U, and numerous other models spanning multiple series and generations. The buffer overflow occurs due to insufficient bounds checking when concatenating device information strings, creating a condition where attacker-controlled input can overwrite adjacent memory locations on the stack.
The technical exploitation of this vulnerability leverages the improper string handling mechanism within the network discovery process. When remote attackers send specially crafted device information packets containing excessively long strings, the strcat function blindly appends this data to a fixed-size buffer without verifying the destination capacity. This classic stack buffer overflow allows attackers to overwrite return addresses, function pointers, and other critical stack variables, potentially enabling arbitrary code execution with the privileges of the affected process. The vulnerability is particularly dangerous because it operates during normal network discovery procedures, meaning attackers can exploit it without requiring physical access or prior authentication to the device. According to CWE classification, this represents a CWE-121 stack-based buffer overflow, which is categorized under the broader weakness of insufficient boundary checking.
The operational impact of CVE-2017-11420 extends beyond simple code execution to encompass complete device compromise and potential network infiltration. Successful exploitation can result in persistent backdoor access, data exfiltration, and the ability to use compromised devices as launch points for attacks against other network systems. The vulnerability affects devices running firmware versions where the network discovery service remains active, potentially exposing thousands of consumer and enterprise routers to remote exploitation. Network attackers can leverage this vulnerability through standard network traffic analysis and packet crafting techniques, making it particularly dangerous for unpatched networks. The ATT&CK framework categorizes this as a privilege escalation technique through software exploitation, potentially enabling lateral movement within network environments. The widespread deployment of affected ASUS router models means that the attack surface is extensive, with many devices remaining unpatched in production environments.
Mitigation strategies for this vulnerability require immediate firmware updates from ASUS to address the buffer overflow in the network discovery component. Network administrators should implement network segmentation to limit the exposure of affected devices and monitor for unusual network discovery traffic patterns. The vulnerability can be partially mitigated through firewall rules that restrict device discovery protocols and network mapping services, though complete protection requires firmware patching. Security monitoring should focus on detecting malformed device information packets and unusual network behavior during discovery operations. Organizations should also consider implementing intrusion detection systems capable of identifying exploitation attempts targeting this specific buffer overflow condition. The remediation process must include comprehensive testing of firmware updates to ensure compatibility with existing network configurations while addressing the underlying stack buffer overflow in the ASUS_Discovery.c implementation.