Urgent: Critical Vulnerability Discovered in Avast Antivirus for MacOS (CVE-2025-10101)

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Overview

A high-severity vulnerability, identified as CVE-2025-10101, has been discovered in Avast Antivirus for MacOS. This vulnerability is a heap-based buffer overflow, out-of-bounds write that can potentially allow for local execution of code or a denial-of-service (DoS) condition affecting antivirus protection.

This issue affects Avast Antivirus versions from 15.7 up to, but not including, version 3.9.2025.

Technical Details

The vulnerability stems from improper handling of a crafted Mach-O file by the Avast Antivirus engine. Specifically, the parsing of this specially crafted file triggers a heap-based buffer overflow. When processing the malicious Mach-O file, the application writes data beyond the allocated memory buffer on the heap. This out-of-bounds write can corrupt adjacent memory regions, leading to application crashes or, more dangerously, the execution of arbitrary code.

Attackers could exploit this vulnerability by tricking a user into scanning a malicious Mach-O file with the vulnerable version of Avast Antivirus. The execution context is limited to that of the local system, but the impact can be significant.

CVSS Analysis

The Common Vulnerability Scoring System (CVSS) v3.0 score for CVE-2025-10101 is 8.1 (HIGH). This score reflects the high potential impact of the vulnerability.

  • CVSS Score: 8.1
  • Attack Vector (AV): Local (L)
  • Attack Complexity (AC): Low (L)
  • Privileges Required (PR): None (N)
  • User Interaction (UI): Required (R)
  • Scope (S): Unchanged (U)
  • Confidentiality Impact (C): None (N)
  • Integrity Impact (I): High (H)
  • Availability Impact (A): High (H)

The ‘Local’ attack vector indicates that an attacker needs local access to the system to exploit this vulnerability. The ‘Required’ user interaction signifies that a user must perform an action, such as scanning the malicious file, for the exploit to occur. The high integrity and availability impact implies a successful exploit could allow an attacker to modify system files or cause a denial-of-service.

Possible Impact

A successful exploit of CVE-2025-10101 can have the following consequences:

  • Local Code Execution: An attacker may be able to execute arbitrary code on the affected system, potentially gaining control of the machine.
  • Denial of Service: The buffer overflow can lead to a crash of the Avast Antivirus service, resulting in a denial of service and leaving the system unprotected.
  • Data Corruption: Writing beyond the intended buffer may corrupt data, leading to system instability.

Mitigation or Patch Steps

Users of Avast Antivirus for MacOS are strongly advised to update to version 3.9.2025 or later as soon as possible. The update contains a fix for this vulnerability.

  1. Update Avast Antivirus: Open Avast Antivirus and check for updates within the application. Alternatively, download the latest version from the official Avast website.
  2. Verify the Update: After updating, verify that you are running version 3.9.2025 or later.
  3. Exercise Caution: Be cautious when scanning files from untrusted sources.

References

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