CVE-2025-3500 is an integer overflow or wraparound vulnerability identified in Avast Antivirus versions 25.1.981.6 up to but not including 25.3 on Windows platforms. The root cause lies in improper validation and handling of integer arithmetic within the antivirus software, leading to an overflow condition. This flaw can be exploited by a local attacker with limited privileges who can induce the overflow through crafted inputs or operations that the antivirus processes. The overflow can corrupt memory or bypass security checks, enabling privilege escalation to SYSTEM or equivalent high-level privileges. The vulnerability requires user interaction, such as running a malicious file or triggering a specific scan, but the attack complexity is low and no specialized conditions are needed. The CVSS v3.1 score of 9.0 reflects the critical impact on confidentiality, integrity, and availability, with network attack vector, low attack complexity, and partial privileges required. Although no public exploits are known yet, the vulnerability's nature and severity make it a high-risk issue. The affected product is widely used in Europe, especially in enterprise and consumer environments, making it a significant threat vector. The vulnerability is categorized under CWE-190 (Integer Overflow or Wraparound), a common software weakness that can lead to memory corruption and arbitrary code execution if not properly mitigated.

For European organizations, this vulnerability poses a significant risk of local privilege escalation, potentially allowing attackers to gain full control over affected Windows systems running vulnerable Avast Antivirus versions. This can lead to unauthorized access to sensitive data, disruption of critical services, and deployment of further malware or ransomware. Enterprises relying on Avast for endpoint protection may face compromised security postures, undermining trust in their defenses. The impact extends to confidentiality, integrity, and availability of systems, with potential cascading effects on business operations and regulatory compliance, especially under GDPR. The requirement for user interaction limits remote exploitation but does not eliminate risk, as social engineering or insider threats could trigger the exploit. The absence of known exploits currently provides a window for proactive mitigation, but the critical severity demands urgent patching and monitoring. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly vulnerable due to the high value of their data and systems.

1. Immediately upgrade Avast Antivirus to version 25.3 or later once the patch is released to remediate the integer overflow vulnerability. 2. Until patching is possible, restrict local user privileges to the minimum necessary, preventing unprivileged users from executing potentially malicious files or triggering scans. 3. Implement application whitelisting to limit execution of unauthorized binaries that could exploit the vulnerability. 4. Educate users about the risks of opening unknown files or running untrusted software to reduce the likelihood of user interaction exploitation. 5. Monitor endpoint logs and antivirus alerts for unusual activity indicative of privilege escalation attempts. 6. Employ endpoint detection and response (EDR) solutions to detect and block suspicious behaviors related to memory corruption or privilege escalation. 7. Coordinate with Avast support and subscribe to security advisories to receive timely updates and guidance. 8. Conduct internal vulnerability assessments and penetration tests focusing on privilege escalation vectors to identify and remediate similar weaknesses. 9. Enforce strict network segmentation to limit lateral movement if a system is compromised. 10. Backup critical data regularly and verify restore procedures to mitigate impact of potential attacks leveraging this vulnerability.