CVE-2025-10101 is a heap-based buffer overflow vulnerability identified in Avast Antivirus for MacOS, specifically affecting versions from 15.7 up to but not including the patch release 3.9.2025. The flaw is triggered by processing a specially crafted Mach-O file, the native executable format on MacOS. This improper handling leads to an out-of-bounds write in the heap memory, which can corrupt memory structures and enable an attacker to execute arbitrary code with the privileges of the antivirus process or cause a denial of service by crashing the antivirus software. The vulnerability requires local access, has a high attack complexity, and does not require privileges or user interaction, indicating that an attacker must already have some foothold on the system but does not need elevated rights or user actions to exploit. The scope is classified as changed, meaning the vulnerability can affect resources beyond the initially compromised component. The impact on confidentiality, integrity, and availability is high, as successful exploitation can lead to full compromise of the antivirus functionality, potentially allowing malware to evade detection or disable protection entirely. No public exploits have been reported yet, but the high CVSS score (8.1) underscores the critical nature of this vulnerability. The lack of patch links suggests that a fix is pending or recently released, emphasizing the need for vigilance. The vulnerability is tracked under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), both indicating memory corruption issues. Given Avast's widespread use in Europe and the prevalence of MacOS in enterprise and professional environments, this vulnerability poses a significant risk to organizations relying on Avast Antivirus for endpoint protection on Mac devices.

For European organizations, the impact of CVE-2025-10101 is substantial. Successful exploitation can lead to local code execution with the antivirus process privileges, potentially allowing attackers to disable or bypass antivirus defenses, leading to undetected malware infections. This compromises the confidentiality and integrity of sensitive data and can disrupt business operations through denial of service. Organizations with MacOS endpoints running affected Avast versions are particularly vulnerable. The threat is heightened in sectors with stringent security requirements such as finance, healthcare, and government, where antivirus protection is critical. Additionally, the ability to execute code locally without user interaction or elevated privileges increases the risk from insider threats or attackers who have gained initial access through other means. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate it, as proof-of-concept or weaponized exploits could emerge. The vulnerability also challenges incident response and forensic efforts by potentially disabling security tools. Overall, the threat could lead to significant operational disruption, data breaches, and regulatory compliance issues under European data protection laws.

1. Immediate patching: Monitor Avast’s official channels for the release of the security update addressing CVE-2025-10101 and apply it promptly across all MacOS endpoints. 2. Restrict local access: Enforce strict access controls and limit local user privileges to reduce the risk of exploitation by unauthorized or low-privileged users. 3. Application whitelisting: Implement application control policies to prevent execution of untrusted or suspicious Mach-O files. 4. Endpoint monitoring: Deploy advanced endpoint detection and response (EDR) solutions capable of detecting anomalous behavior related to antivirus process crashes or memory corruption. 5. Network segmentation: Isolate MacOS systems running Avast Antivirus to contain potential compromises and limit lateral movement. 6. User training: Educate users about the risks of executing unknown files locally and encourage reporting of unusual system behavior. 7. Incident readiness: Prepare incident response plans specifically addressing antivirus failures and potential malware bypass scenarios. 8. Regular audits: Conduct frequent security audits and vulnerability assessments focusing on endpoint protection software configurations and update status. These measures, combined with timely patching, will significantly reduce the risk posed by this vulnerability.