CVE-2022-36610 in A720R
Summary
by MITRE • 08/29/2022
TOTOLINK A720R V4.1.5cu.532_B20210610 was discovered to contain a hardcoded password for root at /etc/shadow.sample.
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Analysis
by VulDB Data Team • 10/09/2022
The vulnerability identified as CVE-2022-36610 represents a critical security flaw in the TOTOLINK A720R router firmware version V4.1.5cu.532_B20210610. This issue stems from the presence of a hardcoded administrative password within the device's configuration files, specifically located at the /etc/shadow.sample path. The existence of such hardcoded credentials violates fundamental security principles and creates an immediate and severe risk for any device running this firmware version. The vulnerability is categorized under CWE-798 as the use of hardcoded credentials, which is one of the most straightforward yet dangerous security misconfigurations in network devices. This flaw directly enables unauthorized remote access to the device with administrative privileges, as the password is embedded within the firmware itself rather than being dynamically generated or user-configured. The hardcoded nature means that this credential remains constant across all devices running the affected firmware, making it a prime target for automated exploitation campaigns.
The technical implementation of this vulnerability involves the device's firmware containing a pre-defined root password that is stored in plaintext within the shadow sample file. This configuration file typically contains hashed passwords for system accounts, but in this case, the root account has been configured with a predictable and well-known password. The presence of such credentials in the firmware means that any attacker who can access the device's file system or network interface can gain immediate administrative control. The vulnerability is particularly concerning because it affects the device's authentication mechanism at the most fundamental level, bypassing any user-defined security measures that might otherwise be in place. Network security professionals should note that this type of vulnerability often relates to the ATT&CK technique T1210 - Exploitation of Remote Services, where attackers leverage weak or hardcoded credentials to gain access to network infrastructure. The impact extends beyond simple unauthorized access, as the attacker now possesses complete control over the router's configuration, potentially enabling man-in-the-middle attacks, DNS hijacking, or the establishment of persistent backdoors.
The operational impact of this vulnerability is severe and far-reaching for organizations and individuals using affected TOTOLINK A720R devices. Once exploited, the attacker can modify network configurations, redirect traffic through malicious servers, or establish covert communication channels that can remain undetected for extended periods. The router becomes a potential entry point for broader network infiltration, as it often serves as a gateway for network traffic and may have access to sensitive internal systems. The vulnerability affects all devices running the specific firmware version mentioned, creating a massive attack surface that can be exploited by automated scanning tools. Security teams must understand that this vulnerability is not just a single point of failure but a systemic weakness that undermines the integrity of the entire network infrastructure. The issue is particularly problematic in environments where network segmentation is intended to isolate sensitive data, as the compromised router can serve as a bridge between network zones. Organizations should consider this vulnerability in their risk assessments and implement immediate remediation measures, as the hardcoded nature of the password means that no amount of password rotation or user management can address the root cause. The ATT&CK framework identifies this as a critical weakness in the initial access phase, where attackers can leverage such credentials to establish persistent access to network resources. This vulnerability also highlights the importance of firmware security testing and the need for manufacturers to implement proper credential management practices during the development lifecycle.