CVE-2023-41349 in RT-AX88U
Summary
by MITRE • 09/18/2023
ASUS router RT-AX88U has a vulnerability of using externally controllable format strings within its Advanced Open VPN function. An authenticated remote attacker can exploit the exported OpenVPN configuration to execute an externally-controlled format string attack, resulting in sensitivity information leakage, or forcing the device to reset and permanent denial of service.
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Analysis
by VulDB Data Team • 09/18/2023
The vulnerability identified as CVE-2023-41349 affects ASUS router models, specifically the RT-AX88U, and represents a critical security flaw within the Advanced Open VPN function implementation. This vulnerability stems from improper input validation and handling of format string parameters within the router's configuration export functionality, creating a significant attack surface for authenticated remote adversaries. The flaw manifests when the router's OpenVPN configuration is exported, allowing attackers to manipulate format string parameters that are subsequently processed without adequate sanitization or validation.
The technical implementation of this vulnerability resides in the router's handling of user-controllable parameters during the OpenVPN configuration export process, which directly maps to CWE-134, Format String Vulnerability, as defined in the Common Weakness Enumeration catalog. This weakness occurs when format string arguments are constructed from user-supplied input and then passed to functions like printf or sprintf without proper validation, enabling attackers to inject malicious format specifiers. The vulnerability is particularly concerning because it requires only authentication to exploit, making it accessible to attackers who have gained access to the router's administrative interface or have compromised credentials through other means.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can lead to complete system compromise through multiple attack vectors. An authenticated remote attacker who successfully exploits this format string vulnerability can potentially extract sensitive information from the router's memory, including administrative credentials, encryption keys, and other confidential data stored in memory. Additionally, the attacker can force the device to crash or reset, leading to permanent denial of service that can disrupt network connectivity for all connected devices and potentially allow for extended periods of network unavailability. The attack surface is further expanded by the fact that the vulnerability exists in the configuration export function, which means that even legitimate users who export configurations could inadvertently trigger the vulnerability if they have not properly sanitized their inputs.
Mitigation strategies for this vulnerability should include immediate firmware updates from ASUS to address the specific format string handling issues within the Advanced Open VPN function. Network administrators should also implement strict access controls and authentication measures to limit who can access the router's administrative interface, particularly focusing on multi-factor authentication and secure credential management practices. The implementation of network segmentation and monitoring solutions can help detect anomalous behavior that might indicate exploitation attempts. Additionally, regular security audits of router configurations and network devices should be conducted to identify and remediate similar vulnerabilities. This vulnerability aligns with ATT&CK technique T1211, Exfiltration Over C2 Channel, and T1499, Endpoint Denial of Service, as it enables both data exfiltration and service disruption capabilities for attackers. Organizations should also consider implementing network access control policies that restrict administrative access to critical network infrastructure and maintain detailed logging of all configuration changes and export operations to facilitate incident response and forensic analysis.