CVE-2026-3091 in Presto Client
Summary
by MITRE • 02/24/2026
An uncontrolled search path element vulnerability in Synology Presto Client before 2.1.3-0672 allows local users to read or write arbitrary files and conduct denial-of-service during installation by placing a malicious DLL in advance in the same directory as the installer.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified as CVE-2026-3091 represents a critical uncontrolled search path element flaw within the Synology Presto Client software ecosystem. This issue affects versions prior to 2.1.3-0672 and stems from the installer's improper handling of dynamic link library loading mechanisms during the installation process. The fundamental technical weakness lies in the software's failure to properly validate or sanitize the search path used to locate required DLL files, creating an exploitable condition that can be leveraged by local attackers with minimal privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables arbitrary file read and write operations through a carefully crafted malicious DLL placement. Attackers can position their malicious payload in the same directory as the installer, exploiting the predictable search order behavior to load their code instead of legitimate system libraries. This technique directly maps to CWE-427 Uncontrolled Search Path Element, which specifically addresses the dangerous practice of allowing external code to be loaded through insecure search path configurations. The vulnerability's exploitation requires only local access and basic file system manipulation capabilities, making it particularly concerning for environments where user privileges are not strictly controlled.
From a security perspective, this vulnerability aligns with several ATT&CK tactics including privilege escalation and persistence mechanisms. The attack vector leverages the legitimate installer process to execute malicious code, potentially bypassing traditional security controls that might monitor network-based attacks. The installation phase becomes a critical window where adversaries can establish persistent access or escalate privileges within the system. The vulnerability's remediation requires proper input validation and secure coding practices that ensure dynamic library loading occurs through controlled, validated paths rather than relying on potentially compromised search paths.
The exploitation scenario involves placing a malicious DLL with the same name as a legitimate system DLL in the installer's directory, causing the installation process to load the attacker-controlled code. This approach demonstrates how seemingly benign installation processes can become attack vectors when proper security controls are absent. Organizations should implement immediate mitigations including updating to version 2.1.3-0672 or later, implementing proper access controls on installation directories, and conducting thorough security reviews of third-party installation processes. The vulnerability also highlights the importance of secure coding practices and proper DLL loading mechanisms that should be enforced through automated code analysis tools and security testing procedures to prevent similar issues in other software components.