CVE-2025-6139 is a security vulnerability identified in the TOTOLINK T10 router, specifically affecting version 4.1.8cu.5207. The issue arises from the use of a hard-coded password embedded within the device's /etc/shadow.sample file, which is a critical system file typically used to store hashed user passwords on Unix-like systems. This hard-coded password can potentially be exploited by an attacker who has access to the local network where the device operates. The vulnerability is classified as problematic but with a low CVSS score of 2.0, indicating limited severity. The attack complexity is high, meaning that exploitation requires significant effort, skill, or specific conditions. Additionally, exploitation does not require user interaction but does require high privileges (PR:H), and the attack vector is local (AV:A), meaning the attacker must already have access to the local network environment. The impact on confidentiality, integrity, and availability is low, and there is no known exploit in the wild at this time. The vulnerability was publicly disclosed on June 16, 2025, and while the exploit details are available, the difficulty of exploitation reduces the immediate risk. The lack of available patches or vendor advisories suggests that mitigation may currently rely on network-level controls and configuration adjustments. Overall, this vulnerability represents a potential risk primarily in scenarios where an attacker has local network access and can leverage the hard-coded password to escalate privileges or gain unauthorized access to the device's administrative functions.

For European organizations, the impact of CVE-2025-6139 is generally limited due to the low severity and the requirement for local network access and high privileges to exploit the vulnerability. However, in environments where TOTOLINK T10 routers are deployed, especially in smaller offices or branch locations with less stringent network segmentation, this vulnerability could allow an insider threat or a compromised device within the local network to gain unauthorized access to the router. This could lead to potential unauthorized configuration changes, interception of network traffic, or pivoting to other internal systems. The low impact on confidentiality, integrity, and availability means that widespread disruption or data breaches are unlikely solely due to this vulnerability. Nevertheless, in critical infrastructure or sensitive environments where TOTOLINK devices are used, even low-severity vulnerabilities can contribute to a larger attack chain. The absence of known exploits in the wild reduces immediate risk, but public disclosure means attackers could develop exploits over time. European organizations should be aware of this vulnerability, especially those using TOTOLINK T10 routers in their network infrastructure, and assess their exposure accordingly.

1. Network Segmentation: Ensure that TOTOLINK T10 devices are placed in isolated network segments with strict access controls to limit local network exposure. 2. Access Control: Restrict administrative access to the router to trusted personnel and devices using MAC address filtering, VPNs, or management VLANs. 3. Firmware Updates: Regularly check for firmware updates from TOTOLINK or authorized vendors, and apply patches promptly once available. 4. Password Management: Change any default or hard-coded passwords immediately if accessible, and enforce strong, unique passwords for all administrative accounts. 5. Monitoring and Logging: Enable detailed logging on the router and monitor for unusual access patterns or configuration changes that could indicate exploitation attempts. 6. Network Intrusion Detection: Deploy IDS/IPS solutions capable of detecting anomalous activities within the local network that might indicate attempts to exploit this vulnerability. 7. Physical Security: Ensure physical security of network devices to prevent unauthorized local access. 8. Vendor Engagement: Engage with TOTOLINK support channels to request official patches or guidance regarding this vulnerability. 9. Device Replacement: Consider replacing TOTOLINK T10 devices with more secure alternatives if mitigation options are insufficient or if the devices are critical to network security.