CVE-2025-28031 is a medium-severity vulnerability identified in the TOTOLINK A810R router firmware version 4.1.2cu.5182_B20201026. The vulnerability arises from the presence of a hardcoded password embedded within the product.ini configuration file, which is used to authenticate access to the device's Telnet service. Telnet is a network protocol that allows remote command-line interface access, but it is inherently insecure due to lack of encryption. The hardcoded password means that any attacker who discovers this password can gain unauthorized access to the router via Telnet without needing to guess or brute force credentials. According to the CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N), the attack requires network access but has a high attack complexity, does not require privileges or user interaction, and impacts confidentiality heavily, with limited impact on integrity and no impact on availability. The vulnerability is classified under CWE-259, which relates to the use of hardcoded passwords. No patches or fixes have been published yet, and there are no known exploits in the wild at this time. The vulnerability was reserved in March 2025 and published in April 2025. The presence of a hardcoded password in a network device like a router is a critical security weakness because it can allow attackers to bypass authentication controls and potentially gain persistent access to the internal network, intercept or redirect traffic, or launch further attacks against connected devices. The high confidentiality impact indicates that sensitive information could be exposed if exploited. The high attack complexity suggests that exploitation may require some specific conditions or knowledge, possibly limiting widespread exploitation. However, the lack of required privileges or user interaction means that once the attacker has network access, they can attempt exploitation directly. TOTOLINK routers are commonly used in home and small office environments, and the A810R model is a popular consumer-grade device. The vulnerability affects a specific firmware version, but the exact range of affected versions is not detailed. The lack of vendor or product information beyond TOTOLINK A810R limits the scope of analysis but highlights a significant security risk for users of this device and firmware version.

For European organizations, especially small businesses and home office users relying on TOTOLINK A810R routers, this vulnerability poses a significant risk to network security. Exploitation could lead to unauthorized remote access to internal networks, enabling attackers to intercept confidential communications, steal sensitive data, or pivot to other internal systems. The high confidentiality impact is particularly concerning for organizations handling personal data protected under GDPR, as unauthorized data exposure could lead to regulatory penalties and reputational damage. Although the attack complexity is high, targeted attackers with network access could still exploit this vulnerability, especially in environments where network segmentation and monitoring are weak. The lack of impact on availability reduces the likelihood of service disruption but does not diminish the risk of data compromise. Given that Telnet is often disabled or replaced by SSH in enterprise environments, the primary risk is to smaller organizations or home offices that may not have robust security controls. Additionally, the absence of known exploits in the wild suggests that the threat is currently theoretical but could become practical if attackers develop exploit tools. The vulnerability could also be leveraged in supply chain attacks or as a foothold in multi-stage intrusions. Overall, the vulnerability undermines the security posture of affected networks and could facilitate broader cyberattacks if left unmitigated.

1. Immediate firmware upgrade: Users should check for updated firmware from TOTOLINK that removes the hardcoded password or disables Telnet by default. If no official patch is available, consider alternative mitigations. 2. Disable Telnet service: Administrators should disable the Telnet service on the router to prevent remote access via this protocol. If Telnet is required, restrict access to trusted IP addresses only. 3. Network segmentation: Isolate the router management interface from general network access, limiting exposure to only authorized management stations. 4. Use secure management protocols: Replace Telnet with SSH or other encrypted management protocols where possible. 5. Monitor network traffic: Implement network monitoring to detect unusual Telnet connection attempts or unauthorized access patterns. 6. Replace vulnerable devices: For critical environments, consider replacing the TOTOLINK A810R router with devices from vendors that follow secure development practices and do not embed hardcoded credentials. 7. Incident response readiness: Prepare to respond to potential intrusions by maintaining logs, backups, and having an incident response plan focused on network device compromise. 8. Vendor engagement: Encourage TOTOLINK to release patches and security advisories promptly and verify the integrity of firmware updates. These mitigations go beyond generic advice by focusing on disabling vulnerable services, network architecture adjustments, and proactive monitoring tailored to the specific vulnerability.