CVE-2025-3500 is an integer overflow or wraparound vulnerability categorized under CWE-190, found in Avast Antivirus version 25.1.981.6 running on Windows platforms. The vulnerability occurs due to improper validation or handling of integer values within the antivirus software, which can cause arithmetic operations to overflow and wrap around, resulting in unexpected behavior. This flaw can be exploited by an attacker with limited privileges (PR:L) and requires user interaction (UI:R), such as tricking a user into performing an action that triggers the vulnerability. The exploitation leads to privilege escalation, allowing the attacker to gain higher-level system privileges than originally permitted. The CVSS 3.1 base score is 9.0 (critical), reflecting the vulnerability’s network attack vector (AV:N), low attack complexity (AC:L), and the scope change (S:C), meaning the impact extends beyond the vulnerable component. The impact affects confidentiality, integrity, and availability (all rated high), potentially allowing full system compromise. Although no public exploits are known at this time, the vulnerability’s characteristics make it a high-risk issue. The vulnerability affects Avast Antivirus versions from 25.1.981.6 up to but not including 25.3, indicating that the vendor has likely addressed the issue in the 25.3 release. No patch links are currently provided, so organizations must monitor Avast’s official channels for updates. The flaw’s exploitation could be leveraged in targeted attacks or malware campaigns aiming to bypass antivirus protections and escalate privileges on Windows endpoints.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Avast Antivirus on Windows systems in both enterprise and consumer environments. Successful exploitation could allow attackers to escalate privileges, bypass security controls, and gain persistent access to critical systems. This can lead to data breaches, disruption of services, and potential lateral movement within networks. Sectors such as finance, healthcare, government, and critical infrastructure are particularly vulnerable due to the sensitivity of their data and the potential impact of system compromise. The vulnerability’s network attack vector and low complexity mean that attackers can exploit it remotely with minimal effort, increasing the likelihood of exploitation in the wild once exploit code becomes available. The requirement for user interaction slightly reduces the risk but does not eliminate it, as social engineering or phishing could facilitate triggering the vulnerability. The scope change indicates that the compromise could extend beyond the antivirus process, affecting the entire system’s security posture. Overall, the vulnerability threatens confidentiality, integrity, and availability of affected systems, making it a critical concern for European cybersecurity defenses.

1. Immediately upgrade Avast Antivirus to version 25.3 or later once it becomes available, as this version addresses the vulnerability. 2. Until a patch is applied, restrict user privileges to the minimum necessary to reduce the risk of privilege escalation. 3. Implement strict application whitelisting and endpoint protection policies to detect and block suspicious activities related to privilege escalation attempts. 4. Educate users about the risks of social engineering and phishing attacks that could trigger the required user interaction for exploitation. 5. Monitor system and security logs for unusual privilege escalation events or unexpected behavior in Avast processes. 6. Employ network segmentation to limit lateral movement if a system is compromised. 7. Use advanced threat detection tools capable of identifying exploitation attempts targeting antivirus software. 8. Coordinate with Avast support and subscribe to their security advisories to receive timely updates and patches. 9. Conduct regular vulnerability assessments and penetration testing focusing on endpoint security controls. 10. Consider deploying additional layers of security such as behavior-based detection to complement antivirus protections.