CVE-2023-34359 in RT-AX88U
Summary
by MITRE • 07/31/2023
ASUS RT-AX88U's httpd is subject to an unauthenticated DoS condition. A remote attacker can send a specially crafted request to the device which causes the httpd binary to crash within the "do_json_decode()" function of ej.c, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 07/31/2023
The vulnerability identified as CVE-2023-34359 affects ASUS RT-AX88U routers and represents a critical denial of service weakness in the device's web server implementation. This issue stems from an insufficient input validation mechanism within the httpd binary that processes JSON data submitted through web requests. The flaw specifically manifests within the do_json_decode() function located in the ej.c source file, where malformed or specially crafted JSON payloads can trigger unexpected behavior leading to complete service disruption. The vulnerability is particularly concerning because it requires no authentication credentials to exploit, making it accessible to any remote attacker with network connectivity to the affected device.
The technical implementation of this vulnerability involves a classic buffer overflow or parsing error condition that occurs when the httpd service attempts to process malformed JSON input. When a remote attacker sends a crafted HTTP request containing malformed JSON data to the router's web interface, the do_json_decode() function fails to properly handle the unexpected input structure. This failure results in a segmentation fault or similar memory corruption issue that causes the httpd process to terminate abruptly. The root cause aligns with CWE-129, which describes improper validation of array index values, and CWE-248, which covers exposure of exception information. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004, which involves network denial of service attacks targeting network infrastructure devices.
The operational impact of this vulnerability extends beyond simple service interruption as it can render the entire router inaccessible to legitimate users and administrators. Network availability is compromised because the web-based management interface becomes unavailable, preventing users from configuring or monitoring their network settings. This affects both local network operations and remote management capabilities, as administrators cannot access the device through its standard web interface to address the issue or implement security measures. The DoS condition may persist until the device is manually rebooted or the httpd service is restarted, creating extended downtime for network operations. Organizations relying on these devices for network infrastructure management face significant operational disruption, particularly in environments where router accessibility is critical for maintaining network connectivity and security posture.
Mitigation strategies for this vulnerability should focus on immediate network segmentation and access control measures. Network administrators should implement firewall rules that restrict access to the router's web management interface to trusted IP addresses only, reducing the attack surface available to remote attackers. The most effective long-term solution involves applying the vendor-provided firmware update that patches the JSON parsing logic in the httpd binary. Additionally, implementing network monitoring solutions that can detect unusual traffic patterns or service disruptions can help identify exploitation attempts. Organizations should also consider disabling unnecessary web management interfaces when not actively required, and implementing robust network access controls through network segmentation to limit the potential impact of such vulnerabilities. The vulnerability highlights the importance of maintaining current firmware versions and implementing regular security assessments of network infrastructure devices to prevent similar issues from compromising network availability and security.