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 3.9.2025. The flaw occurs during the processing of crafted Mach-O files, which are executable file formats used by macOS. This vulnerability allows an attacker with local access to perform an out-of-bounds write on the heap, leading to memory corruption. The consequences of this memory corruption include the possibility of arbitrary code execution with the privileges of the antivirus process or causing a denial of service by crashing the antivirus software. The vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). The CVSS v3.1 score is 8.1, indicating high severity, with an attack vector limited to local (AV:L), high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), and scope changed (S:C), impacting confidentiality, integrity, and availability (C:H/I:H/A:H). No public exploits are known at this time, but the vulnerability poses a significant risk because compromising the antivirus can disable or subvert endpoint protection, potentially allowing further compromise of the host system. The lack of a patch link suggests that a fix is pending or not yet publicly released. This vulnerability highlights the risk of processing untrusted executable files locally and the importance of secure parsing routines in security software.

For European organizations, this vulnerability presents a critical risk to endpoint security on macOS devices protected by Avast Antivirus. Successful exploitation could allow attackers to execute arbitrary code locally, potentially disabling antivirus defenses or gaining persistence on critical systems. This undermines the confidentiality, integrity, and availability of sensitive data and systems. Sectors with high macOS usage, such as creative industries, finance, and technology firms, are particularly vulnerable. The denial of service aspect could disrupt antivirus operations, increasing exposure to other malware. Since exploitation requires local access, insider threats or compromised user accounts could be leveraged. The vulnerability could also be chained with other exploits to escalate privileges or move laterally within networks. Given Avast's market presence in Europe, especially in countries with strong macOS adoption, the threat could have widespread operational and reputational impacts.

Organizations should prioritize updating Avast Antivirus to the latest patched version as soon as it becomes available. Until a patch is released, restrict local access to macOS systems running vulnerable Avast versions by enforcing strict access controls and monitoring for suspicious activity involving Mach-O files. Employ endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. Educate users about the risks of executing or opening untrusted files locally. Implement application whitelisting to limit execution of unauthorized Mach-O binaries. Regularly audit antivirus logs for crashes or unusual behavior that may indicate exploitation attempts. Coordinate with Avast support for timely updates and advisories. Consider temporary alternative antivirus solutions if patching is delayed. Finally, maintain robust backup and incident response plans to quickly recover from potential compromise.