CVE-2025-10905 is a vulnerability classified under CWE-693 (Protection Mechanism Failure) affecting the MiniFilter driver component of Avast Free Antivirus on Windows platforms before version 25.9. The MiniFilter driver is responsible for filtering file system operations to provide real-time protection against malware. Due to a collision issue within this driver, a local attacker who already has administrative privileges can exploit this flaw to disable Avast's real-time protection and self-defense features. This effectively removes the antivirus's ability to detect and block malicious activities, leaving the system vulnerable to further compromise. The vulnerability does not allow privilege escalation or direct data compromise but undermines the availability and reliability of the protection mechanisms. The CVSS 3.1 base score is 4.4 (medium), reflecting the requirement for high privileges (local administrative access) and no user interaction. No public exploits or patches are currently available, indicating that the vulnerability is newly disclosed and not yet actively exploited. The flaw highlights the importance of robust protection mechanisms in security software, as failure in these components can severely impact endpoint security posture.

For European organizations, this vulnerability poses a risk primarily to the availability and effectiveness of endpoint protection on Windows systems running Avast Free Antivirus. If exploited, attackers with administrative access could disable antivirus defenses, facilitating subsequent malware infections, data destruction, or lateral movement within networks. This could lead to increased incident response costs, potential downtime, and exposure to ransomware or other advanced threats. Critical sectors such as finance, healthcare, and government agencies that rely on Avast Free Antivirus for endpoint security may face heightened risks. Although exploitation requires local admin privileges, insider threats or attackers who have already gained elevated access could leverage this vulnerability to deepen their foothold. The absence of confidentiality and integrity impacts reduces the risk of direct data breaches from this flaw alone, but the indirect consequences of disabled protection mechanisms can be severe.

1. Restrict administrative privileges strictly to trusted personnel and use the principle of least privilege to minimize the number of users with elevated access. 2. Monitor systems for unusual activity related to driver loading or modifications to antivirus components, using endpoint detection and response (EDR) tools. 3. Implement application whitelisting and driver signing enforcement to prevent unauthorized driver modifications. 4. Regularly audit and review local administrator accounts and their activities. 5. Stay informed about Avast's security advisories and apply patches or updates promptly once they are released to address this vulnerability. 6. Consider deploying complementary security controls such as network segmentation and behavior-based detection to reduce the impact if antivirus protection is disabled. 7. Educate IT staff about this vulnerability and ensure incident response plans include scenarios involving disabled endpoint protection.