CVE-2017-15653 in AsusWRT
Summary
by MITRE
Improper administrator IP validation after his login in the HTTPd server in all current versions (<= 3.0.0.4.380.7743) of Asus asuswrt allows an unauthorized user to execute any action knowing administrator session token by using a specific User-Agent string.
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Analysis
by VulDB Data Team • 02/03/2023
This vulnerability resides in the HTTPd server component of Asus asuswrt firmware versions up to 3.0.0.4.380.7743, representing a critical authentication bypass flaw that undermines the router's security posture. The vulnerability stems from improper validation of administrator IP addresses following successful authentication, creating a path for unauthorized users to escalate privileges and execute administrative actions. The flaw specifically manifests through manipulation of the User-Agent string header, allowing attackers to forge administrative sessions without proper authentication credentials.
The technical implementation of this vulnerability demonstrates a classic case of insufficient access control validation where the system fails to properly verify the source IP address of authenticated administrators. When an administrator logs into the web interface, the system should validate that subsequent requests originate from the same IP address that established the session. However, the asuswrt implementation allows attackers to bypass this validation by crafting specific User-Agent strings that trigger a flawed session handling mechanism. This weakness aligns with CWE-285, which addresses improper authorization in authentication mechanisms, and specifically represents an improper access control vulnerability.
The operational impact of this vulnerability is severe as it enables complete administrative control over affected routers. An attacker who discovers a valid administrator session token can execute arbitrary commands on the device, potentially leading to full network compromise. This includes but is not limited to modifying router configuration, installing malicious firmware, redirecting traffic, or establishing persistent backdoors. The vulnerability's exploitation does not require prior authentication credentials, making it particularly dangerous as it can be exploited by anyone who can observe or intercept a valid session token, potentially through network monitoring or session hijacking techniques.
From a threat modeling perspective, this vulnerability maps to multiple ATT&CK techniques including T1078 for valid accounts and T1059 for command and scripting interpreter usage. The attack surface is significantly expanded because the vulnerability affects all current versions of the firmware, meaning that a large number of devices could be potentially compromised. Network administrators should consider this vulnerability as a high-priority risk since it can be exploited remotely and does not require specialized tools or deep technical knowledge to implement. The attack vector through User-Agent string manipulation also suggests that this vulnerability could be triggered by automated scanning tools, making it particularly dangerous in environments where routers are exposed to the internet.
Mitigation strategies should include immediate firmware updates to versions that address the IP validation flaw, implementation of network segmentation to limit exposure of administrative interfaces, and deployment of intrusion detection systems to monitor for suspicious User-Agent patterns. Additionally, organizations should enforce strict access controls, disable unnecessary administrative services, and implement proper session management practices. The vulnerability highlights the importance of robust input validation and proper access control mechanisms in embedded systems, particularly those handling sensitive administrative functions. Security professionals should also consider implementing network access controls and monitoring for unusual session behavior that might indicate exploitation attempts.