CVE-2025-59366 in ASUS
Summary
by MITRE • 11/25/2025
An authentication-bypass vulnerability exists in AiCloud. This vulnerability can be triggered by an unintended side effect of the Samba functionality, potentially leading to allow execution of specific functions without proper authorization.
Refer to the Security Update for ASUS Router Firmware section on the ASUS Security Advisory for more information.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2025-59366 represents a critical authentication bypass flaw within AiCloud firmware implementations that affects ASUS router products. This security weakness stems from an unintended side effect within the Samba file sharing functionality, creating a pathway for unauthorized access to administrative functions. The vulnerability specifically targets the authentication mechanisms that should normally prevent unauthorized users from executing privileged operations within the router's management interface.
The technical root cause of this issue lies in how the Samba service interacts with the AiCloud authentication framework, creating a condition where legitimate Samba operations can inadvertently trigger authentication bypasses. This occurs when the Samba functionality processes certain requests in a manner that circumvents the normal authentication checks, allowing attackers to access specific administrative functions without proper credentials. The flaw demonstrates poor input validation and insufficient access control implementation, which aligns with CWE-285: Improper Authorization and CWE-305: Authentication Bypass Through User-Controlled Key. The vulnerability essentially creates a backdoor path through the authentication system, enabling attackers to execute functions that should require proper authorization.
The operational impact of this vulnerability is significant, as it allows attackers to gain unauthorized access to router management functions that typically require administrative credentials. This could enable attackers to modify router configurations, access sensitive network data, install malicious software, or establish persistent access to the network. The vulnerability's exploitation potential is heightened by the fact that Samba functionality is commonly enabled on routers for file sharing purposes, making the attack surface more accessible. Attackers could leverage this flaw to perform actions such as changing network settings, modifying firewall rules, accessing stored credentials, or even installing malware on the affected devices.
Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework, particularly under the T1078: Valid Accounts and T1566: Phishing tactics categories. The vulnerability allows for privilege escalation and persistent access, which aligns with techniques used in advanced persistent threat campaigns. Organizations should implement immediate mitigations including disabling Samba functionality when not required, applying the latest firmware updates from ASUS, and implementing network segmentation to limit potential impact. Additional protective measures should include monitoring for unusual Samba activity, implementing strong access controls, and conducting regular security assessments of router configurations. The vulnerability also underscores the importance of proper security testing during software development, particularly for integrated services that interact with authentication systems.