CVE-2026-116596 in Sync
Summary
by MITRE • 10/26/2026
Pyrus Sync for Windows contains a local privilege escalation vulnerability caused by missing authorization controls in its PyrusSyncService Windows service, which allow an attacker with unprivileged access to create files using the ISyncService contract.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified within the Pyrus Sync application for Windows represents a critical flaw in the design of its background synchronization mechanism, specifically residing within the PyrusSyncService component. This local privilege escalation issue stems from a fundamental failure in implementing proper authorization controls when handling file operations through the ISyncService contract interface. In typical software architecture, services running with elevated system privileges must strictly validate user input and enforce access control policies to prevent lower-privileged processes or users from invoking privileged functions. However, in this instance, the service fails to verify whether the calling process possesses the necessary permissions before allowing file creation operations. This oversight creates a direct pathway for an attacker who has already gained unprivileged local access on the target machine to exploit the misconfiguration and escalate their privileges significantly higher within the operating system hierarchy.
From a technical perspective, the core of this vulnerability lies in the improper implementation of security descriptors or access control lists associated with the ISyncService contract. When an application exposes functionality via Windows contracts such as ISyncService, it often runs under a high-privilege context to ensure seamless synchronization across devices without user intervention. The flaw occurs because the service accepts requests from any local user account regardless of their privilege level and executes file creation commands within its own elevated security context. By crafting specific API calls or input parameters that trigger this file creation routine, an attacker can force the system to write files into directories that are normally restricted to administrators or system accounts. This capability effectively bypasses standard Windows permission models, allowing the attacker to manipulate critical system configurations, install malicious software with administrative rights, or modify protected registry keys without detection by default security monitoring tools.
The operational impact of this vulnerability is severe, as it enables a complete compromise of the host machine's integrity and confidentiality once local access is established. An adversary leveraging this flaw can achieve persistent administrative control over the system, facilitating further lateral movement within a network environment or exfiltration of sensitive data stored on the endpoint. This type of privilege escalation is particularly dangerous in enterprise environments where endpoints may be part of larger domain structures, as it allows attackers to pivot from low-level user accounts to high-value targets such as domain controllers or servers hosting critical business applications. Furthermore, because the exploitation relies on legitimate system services and contracts, the activity may evade signature-based detection mechanisms that do not monitor behavioral anomalies in service interactions closely.
To mitigate this risk, immediate remediation should focus on applying vendor-provided patches that address the authorization logic within the PyrusSyncService component. If patching is not immediately feasible, administrators can implement compensating controls by restricting access to the specific executable or DLL associated with the vulnerability using Windows Access Control Lists (ACLs). It is also advisable to disable unnecessary services and enforce strict application whitelisting policies to prevent unauthorized processes from interacting with system contracts. Regular auditing of service permissions and monitoring for unusual file creation events in protected directories can aid in early detection of exploitation attempts. Aligning these remediation efforts with industry standards such as CWE-269, which covers Improper Privilege Management, ensures that the organization addresses not just this specific instance but reinforces broader security hygiene practices to prevent similar privilege escalation vectors in other applications. Additionally, mapping the attack technique to MITRE ATT&CK framework identifiers related to Local Privilege Escalation helps in categorizing the threat accurately and improving incident response playbooks for future occurrences of similar vulnerabilities.