CVE-2015-2851 in Cloud Station
Summary
by MITRE
client_chown in the sync client in Synology Cloud Station 1.1-2291 through 3.1-3320 on OS X allows local users to change the ownership of arbitrary files, and consequently obtain root access, by specifying a filename.
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Analysis
by VulDB Data Team • 11/05/2024
The vulnerability identified as CVE-2015-2851 resides within the Synology Cloud Station client software for macOS, specifically in the client_chown functionality that handles file ownership changes. This flaw exists in versions ranging from 1.1-2291 through 3.1-3320, representing a significant security weakness that affects users running these particular client versions. The vulnerability stems from inadequate input validation and privilege escalation mechanisms within the client application's file management capabilities.
The technical implementation of this vulnerability allows local attackers to exploit the client_chown function by crafting specific filename parameters that bypass normal access controls. When a malicious user provides a specially formatted filename, the application processes this input without proper sanitization or authorization checks, enabling arbitrary file ownership modification. This primitive flaw operates at the system level where the application executes with elevated privileges, making it possible for local users to manipulate file ownership even when they normally lack such permissions. The vulnerability directly relates to CWE-264, which addresses permissions, privileges, and access controls, specifically manifesting as an improper privilege management issue.
The operational impact of this vulnerability extends far beyond simple file ownership changes, as it provides a pathway for local users to escalate their privileges to root access. Once an attacker successfully manipulates file ownership through this vulnerability, they can effectively gain complete system control, allowing them to modify critical system files, install malicious software, or exfiltrate sensitive data. This represents a critical escalation from local privilege escalation to full system compromise, making it particularly dangerous in environments where users may have legitimate access to the system but should not possess administrative privileges. The attack vector is straightforward and does not require network access or complex exploitation techniques, making it easily accessible to threat actors.
Security professionals should immediately recommend that affected organizations assess their Synology Cloud Station client installations and upgrade to versions that address this vulnerability. The remediation process should include comprehensive patch management procedures to ensure all affected systems are updated, along with monitoring for potential exploitation attempts. Organizations should also implement additional controls such as file integrity monitoring and privilege access reviews to detect and prevent unauthorized file ownership changes. This vulnerability aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation, and demonstrates how seemingly minor application flaws can result in complete system compromise. The vulnerability underscores the importance of proper input validation and privilege separation in client applications, particularly those handling file system operations that require elevated permissions.