CVE-2026-27749

High

Published: 05 March 2026

Published

05 March 2026

Modified

01 April 2026

KEV Added

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Patch

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CVSS Score 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0007 20.5th percentile

Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-27749 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Avira Internet Security. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 20.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 AC-6 (Least Privilege) and SI-10 (Information Input Validation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploitation for Privilege Escalation (T1068). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Directly mitigates the deserialization vulnerability by identifying, reporting, and applying vendor patches to eliminate unsafe .NET BinaryFormatter usage in Avira.SystemSpeedup.RealTimeOptimizer.exe.

SI-10 Information Input Validation good match

prevent

Requires validation of untrusted data from the C:\ProgramData file prior to deserialization, preventing execution of arbitrary code from crafted payloads.

AC-6 Least Privilege good match

prevent

Enforces least privilege on the SYSTEM-privileged RealTimeOptimizer.exe process, limiting the scope and impact of privilege escalation from local exploitation.

MITRE ATT&CK Enterprise TechniquesAI

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

Why these techniques?

Unsafe .NET deserialization in a SYSTEM-privileged process (Avira.SystemSpeedup.RealTimeOptimizer.exe) reading attacker-writable files from C:\ProgramData directly enables local privilege escalation to arbitrary code execution as SYSTEM (CWE-502, AV:L/AC:L/PR:L).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Avira Internet Security contains a deserialization of untrusted data vulnerability in the System Speedup component. The Avira.SystemSpeedup.RealTimeOptimizer.exe process, which runs with SYSTEM privileges, deserializes data from a file located in C:\\ProgramData using .NET BinaryFormatter without implementing input validation or deserialization…

safeguards. Because the file can be created or modified by a local user in default configurations, an attacker can supply a crafted serialized payload that is deserialized by the privileged process, resulting in arbitrary code execution as SYSTEM.

Deeper analysisAI

CVE-2026-27749 is a deserialization of untrusted data vulnerability (CWE-502) in Avira Internet Security, specifically within the System Speedup component. The Avira.SystemSpeedup.RealTimeOptimizer.exe process runs with SYSTEM privileges and deserializes data from a file in C:\ProgramData using .NET BinaryFormatter without input validation or safeguards. In default configurations, this file can be created or modified by local users, enabling the vulnerability.

A local attacker with low privileges (PR:L) can exploit this issue with low complexity (AC:L) and no user interaction (UI:N). By placing a crafted serialized payload in the writable file, the attacker triggers deserialization when the privileged process reads it, resulting in arbitrary code execution as SYSTEM. The vulnerability has a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Vendor advisories provide guidance on mitigation and patches, including Avira's support article at https://support.avira.com/hc/en-us/articles/360010656158-Current-Avira-versions, the product page at https://www.avira.com/en/internet-security, and Gen Digital's security advisories at https://www.gendigital.com/us/en/contact-us/security-advisories/.