CVE-2026-27774: Acronis True Image DLL Hijacking Flaw

CVE-2026-27774 Overview

CVE-2026-27774 is a local privilege escalation vulnerability affecting Acronis True Image for Windows. The flaw stems from a DLL hijacking condition (CWE-427: Uncontrolled Search Path Element) that allows a local attacker with limited privileges to escalate their access by placing a malicious DLL in a location where the application searches for libraries during execution.

Critical Impact

A successful exploitation of this vulnerability allows local attackers to escalate privileges from a low-privileged user to potentially SYSTEM-level access, enabling complete system compromise including data theft, malware installation, and persistent backdoor access.

Affected Products

• Acronis True Image (Windows) before build 42902

Discovery Timeline

• April 2, 2026 - CVE-2026-27774 published to NVD
• April 2, 2026 - Last updated in NVD database

Technical Details for CVE-2026-27774

Vulnerability Analysis

This DLL hijacking vulnerability exists due to improper handling of dynamic library loading paths within Acronis True Image for Windows. When the application loads, it searches for required DLL files in multiple directories following the Windows DLL search order. The vulnerability arises because the application searches in directories where a low-privileged user may have write access before checking secure system locations.

The local attack vector requires an attacker to have initial access to the target system with low privileges. The high complexity rating indicates that successful exploitation requires specific conditions to be met, such as timing the DLL placement correctly or requiring user interaction (such as an administrator launching the application after the malicious DLL has been planted).

Upon successful exploitation, the attacker achieves high impact across confidentiality, integrity, and availability—the malicious DLL executes with the privileges of the Acronis True Image process, which typically runs with elevated permissions to perform backup and restore operations.

Root Cause

The root cause of CVE-2026-27774 is classified as CWE-427 (Uncontrolled Search Path Element). The application fails to properly specify or validate the directories from which it loads DLL files. This allows an attacker to place a malicious DLL with the same name as an expected library in a directory that is searched before the legitimate library location. When the application attempts to load the expected DLL, it instead loads and executes the attacker-controlled malicious code.

Attack Vector

The attack vector for this vulnerability is local, requiring the attacker to have existing access to the target system. The exploitation process typically follows these steps:

1. The attacker identifies which DLLs the Acronis True Image application attempts to load and from which directories
2. The attacker places a malicious DLL with the expected filename in a directory that appears earlier in the search path and where they have write permissions
3. When a privileged user (or scheduled task) launches Acronis True Image, the application loads the malicious DLL instead of the legitimate one
4. The malicious code executes with the elevated privileges of the Acronis True Image process

The vulnerability mechanism is well-documented in DLL hijacking attack patterns. For detailed technical information, refer to the Acronis Security Advisory SEC-10057.

Detection Methods for CVE-2026-27774

Indicators of Compromise

• Unexpected DLL files appearing in application directories or user-writable locations within the Acronis True Image installation path
• Process execution anomalies where Acronis True Image processes spawn unexpected child processes or make unusual network connections
• Security events indicating DLL loading from non-standard paths in Windows Event Logs
• File system modifications to directories commonly targeted for DLL hijacking attacks

Detection Strategies

• Monitor for DLL loading events from writable directories using Sysmon Event ID 7 (Image loaded) with focus on Acronis True Image processes
• Implement application whitelisting to detect unauthorized DLLs being loaded by legitimate applications
• Deploy endpoint detection rules to identify suspicious DLL placements in user-accessible directories along the application's search path
• Utilize SentinelOne's behavioral AI to detect privilege escalation attempts and anomalous process behavior

Monitoring Recommendations

• Enable detailed logging for process creation and DLL loading events on systems running Acronis True Image
• Configure alerts for file creation events in directories within the DLL search path of the application
• Regularly audit file permissions on directories in the application's installation path to ensure low-privileged users cannot write to them
• Monitor for lateral movement or persistence mechanisms that may follow successful privilege escalation

How to Mitigate CVE-2026-27774

Immediate Actions Required

• Update Acronis True Image (Windows) to build 42902 or later immediately
• Review file permissions on the Acronis True Image installation directory and ensure only administrators have write access
• Audit systems for any suspicious DLL files that may have been planted in vulnerable locations
• Monitor privileged accounts for signs of compromise following potential exploitation

Patch Information

Acronis has addressed this vulnerability in Acronis True Image for Windows build 42902. Organizations should update to this version or later to remediate the DLL hijacking vulnerability. The security advisory is available at the Acronis Security Advisory SEC-10057 page.

Workarounds

• Restrict write permissions on all directories in the Acronis True Image DLL search path to administrators only
• Implement application control policies to prevent loading of unsigned or untrusted DLLs
• Use Windows Defender Application Control (WDAC) or AppLocker to enforce DLL loading restrictions
• Consider temporarily disabling automatic startup of Acronis True Image services until patching is complete on high-value systems

# Verify Acronis True Image installation directory permissions
icacls "C:\Program Files (x86)\Acronis\TrueImageHome" /T

# Remove write permissions for non-admin users (run as Administrator)
icacls "C:\Program Files (x86)\Acronis\TrueImageHome" /inheritance:r /grant:r Administrators:F /grant:r SYSTEM:F /T