CVE-2025-10905 is a vulnerability identified in the MiniFilter driver component of Avast Free Antivirus for Windows versions prior to 25.9. The MiniFilter driver is responsible for filtering and monitoring file system operations to provide real-time protection. The vulnerability is classified under CWE-693, which relates to protection mechanism failures. Specifically, a collision in the MiniFilter driver allows a local attacker who already possesses administrative privileges on the affected system to disable Avast's real-time protection and self-defense features. This effectively removes critical layers of defense, potentially allowing malware or unauthorized processes to execute without interference from the antivirus software. The attack vector requires local access with high privileges (administrative rights), and no user interaction is necessary to exploit the flaw. The CVSS v3.1 base score is 4.4, reflecting a medium severity primarily due to the requirement for administrative privileges and the lack of impact on confidentiality or integrity directly. The vulnerability affects availability by disabling protection mechanisms, increasing the risk of successful malware infections or persistence. No public exploits have been reported, and no official patches have been linked at the time of publication, though it is expected that Avast will release updates to address this issue. This vulnerability highlights a failure in the protection mechanism designed to safeguard the antivirus software itself, which is critical for maintaining endpoint security integrity.

For European organizations, the primary impact of CVE-2025-10905 lies in the potential degradation of endpoint security posture. By allowing an attacker with administrative privileges to disable real-time protection and self-defense, the vulnerability can facilitate the execution and persistence of malware, ransomware, or other malicious activities without detection. This can lead to increased risk of data loss, operational disruption, and potential lateral movement within networks. Although exploitation requires administrative access, insider threats or attackers who have already escalated privileges could leverage this vulnerability to undermine security controls. The absence of confidentiality and integrity impact reduces the risk of direct data breaches from this flaw alone, but the availability impact can indirectly lead to severe consequences. European organizations with large deployments of Avast Free Antivirus on Windows endpoints, especially in sectors like finance, healthcare, and critical infrastructure, could face increased exposure. The vulnerability also complicates incident response efforts by disabling self-defense mechanisms that protect the antivirus from tampering during an attack.

To mitigate CVE-2025-10905, European organizations should implement the following specific measures: 1) Restrict administrative privileges strictly to trusted personnel and use the principle of least privilege to minimize the number of users with high-level access. 2) Employ robust endpoint detection and response (EDR) solutions that can detect suspicious activities even if antivirus protections are disabled. 3) Monitor system and driver behavior for anomalies indicative of MiniFilter driver tampering or disabling of antivirus components. 4) Enforce application whitelisting and code integrity policies to prevent unauthorized driver modifications. 5) Regularly audit and review administrative access logs to detect potential misuse. 6) Stay vigilant for Avast security advisories and promptly apply patches or updates once they become available to address this vulnerability. 7) Consider deploying layered security controls such as network segmentation and multi-factor authentication to reduce the impact of compromised administrative accounts. 8) Educate administrators on the risks associated with privilege misuse and the importance of maintaining endpoint security hygiene.