CVE-2025-7003: Avira Antivirus Heap Buffer Overflow – Patch Guide

Technical summary

CVE-2025-7003 is a heap buffer out-of-bounds read vulnerability (CWE-125) in the Avira Antivirus scanning engine. When processing a malformed PDF file, the engine fails to properly validate buffer boundaries during memory read operations, allowing an attacker to read beyond allocated heap memory. This can result in information disclosure or trigger an exception leading to denial-of-service of the antivirus process itself. The vulnerability requires user interaction (opening/scanning a malicious PDF) but does not require elevated privileges. It affects Windows, macOS, and Linux platforms running engine versions prior to 8.3.70.56.

Business impact

This vulnerability poses a dual threat to endpoint security posture. First, successful exploitation can disable the antivirus engine on individual systems, leaving them unprotected during an active campaign. Second, if code execution is achieved, an attacker gains local execution capabilities under the privileges of the antivirus process—potentially allowing lateral movement or persistence. For organizations relying on Avira as a primary or supplementary antivirus solution, widespread exposure to malicious PDFs combined with an unpatched Avira version could result in a security gap affecting multiple endpoints simultaneously. The need for user action (file opening) reduces but does not eliminate risk in environments where users routinely handle external documents.

Affected systems

Avira Antivirus on Windows, macOS, and Linux platforms is affected. The vulnerability exists in all engine builds released before version 8.3.70.56. Organizations should inventory all systems running Avira and verify their current engine version against the 8.3.70.56 baseline. Affected versions include both consumer and business editions if they use the vulnerable engine builds.

Exploitability

Exploitation requires crafting a malformed PDF file and delivering it to a target user for scanning or opening. While the vulnerability requires user interaction (UI interaction component in the CVSS vector), the barrier to exploitation is moderate: creating a malicious PDF is within reach of threat actors with basic reverse engineering skills, and social engineering can drive users to open files. The vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, suggesting no widespread active exploitation has been publicly disclosed as of the publication date; however, organizations should not assume this protection will persist. The local attack vector and lack of privilege escalation requirement make this particularly concerning in shared-system or multi-user environments.

Remediation

The definitive fix is to upgrade the Avira Antivirus engine to version 8.3.70.56 or later. Avira typically distributes engine updates through its automatic update mechanism; verify that automatic updates are enabled in your deployment. For enterprise deployments, consult Avira's official advisories and patch management documentation to coordinate rollout across your fleet. Until patching is complete, consider restricting access to untrusted PDF files and educating users to exercise caution when opening PDFs from external sources. Enable any additional scanning hardening options available in your Avira configuration.

Patch guidance

Avira should have released engine version 8.3.70.56 or later to remediate this issue. Verify the exact patch version and availability by consulting the official Avira security advisory and your organization's patch management system. For enterprise customers, confirm patch availability through Avira's vendor portal or contact support for availability on your specific platform (Windows, macOS, Linux). Deploy patches in a controlled manner, testing in a non-production environment first if possible, to ensure compatibility with your systems and other security tools. Monitor Avira's official security advisories for any additional guidance or known issues related to this update.

Detection guidance

Monitor antivirus engine logs and crash dumps for instances of the Avira scanning engine terminating unexpectedly while processing PDF files. System event logs may show access violations or memory protection exceptions tied to the Avira process. Endpoint Detection and Response (EDR) solutions should flag heap corruption or out-of-bounds memory access attempts by the antivirus process itself. Network-based detection is limited unless the malicious PDF is distributed via email or file transfer; focus detection efforts on endpoint telemetry and file content inspection. If available, enable debug or verbose logging in Avira to capture which file triggered the crash, then preserve that file for forensic analysis and vendor notification.

Why prioritize this

This vulnerability merits high priority due to its CVSS score of 7.8 (HIGH severity) and the potential for both denial-of-service and code execution on affected systems. The fact that it can disable the antivirus engine—a critical security control—makes it particularly dangerous in the context of endpoint protection strategy. While exploitation requires user interaction, the ease of social engineering users to open PDFs, combined with the presence of affected versions in many organizations, creates meaningful risk. The absence of active exploitation reports (KEV status: not listed) provides a limited window to patch before broader awareness increases attack likelihood.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) reflects a local vulnerability with low attack complexity, no privilege requirement, and high impact across confidentiality, integrity, and availability. The vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H indicates the attack must originate from the local system (the user must interact with the file), but once triggered, the out-of-bounds read can leak sensitive memory contents or crash the antivirus process entirely. The high impact rating underscores that code execution is theoretically possible, making this a meaningful threat to unpatched systems.

Frequently asked questions