CVE-2021-20164 in AC2600 TEW-827DRU
Summary
by MITRE • 12/31/2021
Trendnet AC2600 TEW-827DRU version 2.08B01 improperly discloses credentials for the smb functionality of the device. Usernames and passwords for all smb users are revealed in plaintext on the smbserver.asp page.
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Analysis
by VulDB Data Team • 01/05/2022
This vulnerability resides in the Trendnet AC2600 TEW-827DRU router firmware version 2.08B01 where sensitive authentication credentials are improperly exposed through the server message block smb functionality. The flaw manifests in the smbserver.asp web page where usernames and passwords for all smb users are displayed in plaintext format, creating a critical security risk for network administrators and end users who rely on these devices for network connectivity and file sharing services.
The technical implementation of this vulnerability stems from inadequate input validation and output sanitization within the web interface components of the router firmware. When users access the smb server configuration page, the application fails to properly mask or encrypt authentication credentials that are stored in the device's configuration files. This represents a direct violation of security best practices and exposes sensitive information that should remain protected within the device's internal memory structures. The vulnerability can be categorized under CWE-200, which specifically addresses the improper exposure of sensitive information, and more broadly aligns with CWE-546, concerning the presence of backdoors or hidden code that could expose system credentials.
The operational impact of this vulnerability extends beyond simple credential disclosure as it fundamentally undermines the security posture of any network utilizing the affected router model. Network administrators who have configured smb shares for file access, printer sharing, or other network services immediately face a risk of unauthorized access to their network resources. Attackers who gain access to the router's web interface can leverage these plaintext credentials to establish unauthorized connections to network shares, potentially escalating privileges and accessing sensitive data stored on networked devices. This vulnerability directly maps to several tactics in the mitre att&ck framework including credential access through credential dumping and privilege escalation via network service exploitation.
The exposure of plaintext credentials creates an immediate and severe risk for organizations that have configured smb services on their network infrastructure. Even if the router itself is not directly exposed to external networks, the presence of these credentials within the device's web interface means that any user with access to the router's administrative interface can extract authentication information for all configured smb users. This creates a potential attack vector that can be exploited by both external adversaries and internal threat actors who may have gained access to legitimate administrative credentials through other means. The vulnerability essentially eliminates the security boundary that should exist between different network services and user accounts, allowing for lateral movement and unauthorized access to network resources that were intended to be protected by proper authentication mechanisms.
Organizations should immediately implement mitigations including disabling smb functionality if not required, implementing network segmentation to isolate the affected devices, and ensuring that administrative interfaces are protected through strong authentication mechanisms. The most effective immediate solution involves updating the firmware to a version that properly handles credential disclosure, though this may not be available for older devices. Network monitoring should be enhanced to detect unauthorized access attempts to the router's web interface, and access controls should be strictly enforced to limit who can reach the administrative configuration pages. Additionally, regular security audits should verify that no sensitive information is exposed through web interfaces, and network administrators should consider implementing network access controls that prevent direct access to administrative interfaces from untrusted networks.