CVE-2025-9091 is a security vulnerability identified in the Tenda AC20 router firmware version 16.03.08.12. The flaw involves the presence of hard-coded credentials within an unspecified functionality related to the file /etc_ro/shadow. This file is typically associated with storing password hashes or authentication data in Unix-like systems, suggesting that the vulnerability could allow unauthorized access if the hard-coded credentials are discovered and exploited. The attack vector is limited to local host access, meaning an attacker must already have some form of local access to the device or network to attempt exploitation. The complexity of the attack is rated as high, and exploitation is considered difficult, which reduces the likelihood of widespread exploitation. The vulnerability does not require user interaction and has a low CVSS score of 2.0, reflecting limited impact and exploitability. No known exploits are currently active in the wild, and no patches or fixes have been linked yet. The vulnerability primarily threatens confidentiality due to potential unauthorized access via hard-coded credentials, but it does not appear to affect integrity or availability directly. The presence of hard-coded credentials is a significant security concern because it can provide persistent unauthorized access if discovered, especially in network devices like routers that serve as gateways to internal networks.

For European organizations, the impact of this vulnerability is relatively limited due to the high complexity and local access requirement for exploitation. However, if an attacker gains local access—such as through physical access, compromised internal devices, or lateral movement within a network—they could leverage the hard-coded credentials to gain unauthorized administrative access to the Tenda AC20 router. This could lead to interception or manipulation of network traffic, potential exposure of sensitive data, and the establishment of persistent footholds within the network. Small and medium enterprises (SMEs) or home offices using Tenda AC20 routers without additional security controls may be more vulnerable. Larger organizations with segmented networks and strict access controls are less likely to be impacted directly. The low severity rating suggests that the vulnerability is not a critical threat but should still be addressed to prevent potential escalation or chaining with other vulnerabilities.

1. Immediate mitigation should include restricting physical and local network access to the Tenda AC20 devices to trusted personnel only, minimizing the risk of local exploitation. 2. Network segmentation should be implemented to isolate routers from general user devices, reducing the attack surface. 3. Monitor network traffic for unusual administrative access attempts or authentication anomalies that could indicate exploitation attempts. 4. Since no official patch is currently available, organizations should contact Tenda support for firmware updates or advisories and apply any released patches promptly. 5. Consider replacing affected Tenda AC20 devices with alternative routers from vendors with stronger security track records if patching is delayed. 6. Implement strong network access controls and use multi-factor authentication on management interfaces where possible to mitigate risks from hard-coded credentials. 7. Regularly audit router configurations and credentials to detect unauthorized changes or the presence of default/hard-coded credentials.