CVE-2026-27749 is a deserialization of untrusted data vulnerability classified under CWE-502, affecting the System Speedup component of Avira Internet Security by Gen Digital Inc. The vulnerability resides in the Avira.SystemSpeedup.RealTimeOptimizer.exe process, which operates with SYSTEM-level privileges on Windows systems. This process deserializes data from a file located in C:\ProgramData using the .NET BinaryFormatter class, which is known to be insecure when handling untrusted input. The core issue is the absence of input validation or deserialization safeguards, allowing an attacker with local user access to create or modify the serialized data file. By crafting a malicious serialized payload, the attacker can trigger the deserialization process to execute arbitrary code with SYSTEM privileges, effectively gaining full control over the affected machine. The vulnerability does not require user interaction or elevated privileges beyond local user access, making it a significant local privilege escalation vector. The CVSS 4.0 base score is 8.5, reflecting high severity due to the combination of high impact on confidentiality, integrity, and availability, and relatively low attack complexity. No patches or mitigations have been officially released at the time of publication, and no known exploits have been observed in the wild. The vulnerability highlights the risks of insecure deserialization practices, especially when privileged processes consume data from locations writable by non-privileged users.

The impact of CVE-2026-27749 is substantial for organizations using Avira Internet Security, particularly those relying on the System Speedup component. Successful exploitation allows an attacker with local user access to escalate privileges to SYSTEM level, granting full control over the affected system. This can lead to unauthorized access to sensitive data, installation of persistent malware, disruption of system operations, and lateral movement within networks. The vulnerability compromises confidentiality, integrity, and availability of affected systems. Organizations with many endpoints running Avira Internet Security are at risk of widespread compromise if attackers gain local access to any machine. The lack of required user interaction or authentication beyond local user privileges lowers the barrier for exploitation in environments where local user accounts may be compromised or shared. Although no known exploits are currently in the wild, the high severity and ease of exploitation make this a critical risk that could be leveraged in targeted attacks or insider threat scenarios.

1. Immediately restrict write permissions on the C:\ProgramData directory and specifically on the file used by Avira.SystemSpeedup.RealTimeOptimizer.exe to prevent unauthorized modification by local users. 2. Monitor and audit changes to files in C:\ProgramData to detect suspicious activity indicative of attempted exploitation. 3. Disable or uninstall the System Speedup component if it is not essential to reduce the attack surface. 4. Apply vendor patches or updates as soon as they become available to address the deserialization flaw. 5. Employ application whitelisting and endpoint detection and response (EDR) solutions to detect and block unauthorized code execution attempts. 6. Educate local users about the risks of executing untrusted code and enforce least privilege principles to limit local user capabilities. 7. Consider deploying host-based intrusion prevention systems (HIPS) that can intercept and block malicious deserialization attempts. 8. Review and harden configuration settings of Avira Internet Security to minimize exposure of privileged processes to untrusted input.