CVE-2016-4982 in authd
Summary
by MITRE
authd sets weak permissions for /etc/ident.key, which allows local users to obtain the key by leveraging a race condition between the creation of the key, and the chmod to protect it.
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Analysis
by VulDB Data Team • 03/04/2025
The vulnerability identified as CVE-2016-4982 affects the authd service component within certain operating systems, specifically targeting the improper handling of file permissions during the creation of authentication keys. This weakness manifests in the /etc/ident.key file which serves as a critical authentication mechanism within the system's identity verification processes. The flaw represents a classic race condition scenario where the timing between file creation and permission setting creates an exploitable window that adversaries can leverage to gain unauthorized access to sensitive authentication credentials.
The technical implementation of this vulnerability stems from the authd service's failure to properly secure the ident.key file immediately upon creation. During the initialization process, the system generates the key file with default permissions before subsequently applying restrictive access controls through chmod operations. This temporal gap between file creation and permission enforcement creates a window where local users can access the unsecured file and extract the authentication key. The race condition occurs because the file is created with permissive permissions, typically allowing read access to all users, before the system applies the intended restrictive permissions that would prevent unauthorized access.
From an operational impact perspective, this vulnerability significantly undermines the security posture of systems relying on authd for authentication services. Local users who exploit this weakness can obtain the ident.key file and subsequently use it to impersonate legitimate system users or gain elevated privileges within the authentication framework. The vulnerability is particularly concerning because it requires minimal privileges to exploit and provides direct access to authentication mechanisms that could enable further lateral movement within the network or privilege escalation attacks. This weakness can be leveraged by attackers who have already gained low-privilege access to the system to escalate their privileges and potentially compromise the entire authentication infrastructure.
The vulnerability aligns with CWE-362, which categorizes race conditions as a critical security weakness, and can be mapped to ATT&CK technique T1552.001 for credentials from password stores and T1068 for exploit for privilege escalation. Organizations should implement immediate mitigations including ensuring that authentication key files are created with restrictive permissions from the outset, eliminating the race condition window through proper file handling procedures. System administrators should also verify that no other similar race conditions exist in authentication or credential management components, and consider implementing additional monitoring to detect unauthorized access attempts to sensitive key files. Regular security audits should validate that all authentication-related files are properly secured during creation and that appropriate access controls are maintained throughout the file lifecycle, preventing attackers from exploiting timing-based vulnerabilities in system initialization processes.