CVE-2018-17022 in GT-AC5300
Summary
by MITRE
Stack-based buffer overflow on the ASUS GT-AC5300 router through 3.0.0.4.384_32738 allows remote attackers to cause a denial of service (device crash) or possibly have unspecified other impact by setting a long sh_path0 value and then sending an appGet.cgi?hook=select_list("Storage_x_SharedPath") request, because ej_select_list in router/httpd/web.c uses strcpy.
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Analysis
by VulDB Data Team • 05/26/2020
The CVE-2018-17022 vulnerability represents a critical stack-based buffer overflow flaw discovered in ASUS GT-AC5300 routers running firmware versions up to 3.0.0.4.384_32738. This vulnerability resides within the web server component of the router's firmware and demonstrates a classic programming error that has significant implications for network security and device availability. The flaw manifests when an attacker crafts a malicious HTTP request containing an excessively long sh_path0 parameter value, which is then processed through the appGet.cgi endpoint with the hook parameter set to select_list("Storage_x_SharedPath"). The vulnerability stems from the improper use of the unsafe strcpy function in the ej_select_list function located in router/httpd/web.c, creating a condition where user-controllable input directly overflows a fixed-size stack buffer without proper bounds checking. This fundamental error in input validation and memory management creates a pathway for remote exploitation that can result in device instability or complete system failure.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common attack methodologies described in the ATT&CK framework under the T1203 technique for legitimate credentials and T1059 command and scripting interpreter categories. When an attacker sends a malformed request with an oversized sh_path0 parameter, the strcpy function blindly copies the input data into a stack buffer that is insufficiently sized to accommodate the input, causing a buffer overflow condition. This overflow corrupts adjacent stack memory, potentially overwriting return addresses, function pointers, or other critical control data structures. The vulnerability's impact extends beyond simple denial of service as indicated in the description, since the unspecified other impacts could include arbitrary code execution or privilege escalation depending on the specific memory corruption patterns and the router's execution environment. The use of strcpy instead of safer alternatives like strncpy or strlcpy represents a CWE-121 stack-based buffer overflow vulnerability that has been consistently flagged as a high-risk programming error in security guidelines.
The operational impact of this vulnerability presents significant risks to network infrastructure and device availability, particularly in enterprise environments where network uptime is critical. A successful exploitation can cause immediate device crashes, forcing network administrators to perform manual restarts or potentially requiring firmware reinstallation to restore functionality. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring physical access or prior authentication, making it particularly dangerous for home and small office networks. Organizations utilizing ASUS GT-AC5300 routers are vulnerable to persistent disruption attacks that could be used for service denial or as a stepping stone for more sophisticated attacks targeting the broader network ecosystem. The vulnerability affects not only the immediate device but also potentially impacts the entire network infrastructure that relies on the router's stable operation for connectivity and security policy enforcement. The exploitation requires minimal technical expertise and can be automated, making it attractive to both opportunistic attackers and organized threat groups seeking to compromise network availability.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from ASUS to address the root cause of the buffer overflow condition. Network administrators should implement network segmentation and access controls to limit exposure of affected devices to untrusted networks while awaiting patch deployment. The implementation of intrusion detection systems that can identify and block malicious requests containing oversized parameters provides an additional layer of defense. Security monitoring should include detection of anomalous traffic patterns that may indicate exploitation attempts, particularly focusing on requests to appGet.cgi with suspicious parameter values. Organizations should also consider implementing web application firewalls to filter potentially malicious requests before they reach the vulnerable router components. The vulnerability highlights the importance of secure coding practices and input validation, with recommendations to replace unsafe string functions like strcpy with their safer counterparts that include bounds checking. Regular vulnerability assessments and firmware update policies should be implemented to address similar issues across the entire network infrastructure, as this vulnerability represents a common class of flaws that can be found in embedded network devices. Additionally, network administrators should conduct regular security audits to identify and remediate similar buffer overflow conditions in other network equipment and applications that may be exposed to similar attack vectors.