CVE-2023-34358 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 a device which contains a specific user agent, causing the httpd binary to crash during a string comparison performed within web.c, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 07/31/2023
The vulnerability identified as CVE-2023-34358 affects ASUS RT-AX88U routers and represents a critical denial of service condition within the device's httpd web server implementation. This flaw exists in the web.c source file where string comparison operations are performed without proper input validation, creating a scenario where an unauthenticated remote attacker can trigger a system crash. The vulnerability specifically targets the user agent string handling mechanism within the httpd binary, which processes incoming HTTP requests from remote clients. When a malicious user agent string is crafted with specific characteristics, the httpd service fails during its string comparison routine, leading to complete service disruption and device unavailability.
The technical exploitation of this vulnerability occurs through a carefully constructed HTTP request that includes a malicious user agent header. The httpd binary in the ASUS RT-AX88U firmware processes this header without adequate bounds checking or sanitization, causing a buffer overflow condition or invalid memory access during the string comparison operation. This type of vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. The flaw demonstrates poor input validation practices where the web server fails to properly handle malformed user agent strings, leading to arbitrary code execution or service termination. The attack vector is particularly dangerous because it requires no authentication credentials, making it accessible to any remote attacker with network connectivity to the affected device.
The operational impact of CVE-2023-34358 extends beyond simple service disruption, as it can result in complete network connectivity loss for devices relying on the affected router. Network administrators may experience extended downtime while troubleshooting the issue, particularly if the DoS condition occurs during critical business hours or when the router serves as a primary network gateway. The vulnerability affects the core web management interface of the router, which means that legitimate users cannot access administrative functions to diagnose or recover from the crash. This condition also creates potential for cascading failures in network infrastructure, as downstream devices may lose connectivity when the primary router becomes unresponsive. The attack can be executed repeatedly, allowing an attacker to maintain persistent denial of service conditions until the device is manually restarted or the firmware is updated.
Mitigation strategies for this vulnerability should include immediate firmware updates from ASUS, which typically address the root cause through proper input validation and bounds checking in the web.c implementation. Network administrators should implement firewall rules to restrict access to the router's web management interface from untrusted networks, though this approach only provides partial protection since the vulnerability can be triggered from any network location. Monitoring systems should be deployed to detect unusual patterns in HTTP traffic that may indicate exploitation attempts, particularly focusing on malformed user agent strings. The ATT&CK framework categorizes this vulnerability under T1499.004, which describes network denial of service attacks, and T1566.002, which covers spearphishing with social engineering techniques. Organizations should also consider implementing network segmentation to isolate critical infrastructure from potentially compromised devices, while maintaining regular vulnerability assessments to identify similar weaknesses in other network components. Additionally, the affected devices should be configured to disable unnecessary web services and implement strong access controls to minimize the attack surface.