CVE-2016-3067 in cygwin
Summary
by MITRE
Cygwin before 2.5.0 does not properly handle updating permissions when changing users, which allows attackers to gain privileges.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2016-3067 affects Cygwin versions prior to 2.5.0 and represents a critical privilege escalation flaw within the Windows compatibility layer. This issue stems from improper handling of file permission updates during user context switches, creating a pathway for malicious actors to elevate their privileges within the system. The vulnerability specifically manifests when the system attempts to change user contexts while maintaining file permissions, leading to potential security boundary violations.
The technical flaw resides in Cygwin's implementation of user privilege management mechanisms where the system fails to correctly validate and update file permissions when transitioning between different user accounts. This misconfiguration allows an attacker to manipulate file access controls and potentially execute arbitrary code with elevated privileges. The underlying issue is classified as a privilege escalation vulnerability that operates at the operating system interface level, where the compatibility layer between Windows and Unix-like systems does not properly enforce access control policies during user switching operations.
From an operational perspective, this vulnerability poses significant risks to systems running affected Cygwin versions, particularly in enterprise environments where privilege escalation can lead to complete system compromise. Attackers can exploit this flaw to gain unauthorized access to restricted resources, escalate their privileges from standard user accounts to administrative levels, and potentially establish persistent access within the network. The vulnerability is particularly concerning because it operates at the system level rather than application level, making detection and mitigation more challenging for security teams.
The impact of this vulnerability extends beyond immediate privilege escalation, as it can serve as a foundation for more sophisticated attacks within the network infrastructure. Organizations utilizing Cygwin for development, testing, or system administration tasks may face severe consequences if this vulnerability remains unpatched, as attackers could leverage it to gain access to sensitive data, modify system configurations, or establish backdoors. This vulnerability aligns with attack patterns documented in the attack tactics and techniques framework, specifically relating to privilege escalation and persistence mechanisms.
Security mitigations for CVE-2016-3067 primarily involve upgrading to Cygwin version 2.5.0 or later, which includes proper permission handling during user context switching. System administrators should also implement additional controls such as monitoring for unauthorized user switching activities, implementing least privilege principles for Cygwin processes, and conducting regular security assessments of compatibility layer implementations. The vulnerability demonstrates the importance of proper access control implementation in cross-platform compatibility layers and serves as a reminder of the critical security considerations when developing system interfaces that bridge different operating system environments. Organizations should also consider implementing network segmentation and monitoring solutions to detect anomalous privilege escalation activities that might indicate exploitation attempts.