CVE-2013-1958 in Linux
Summary
by MITRE
The scm_check_creds function in net/core/scm.c in the Linux kernel before 3.8.6 does not properly enforce capability requirements for controlling the PID value associated with a UNIX domain socket, which allows local users to bypass intended access restrictions by leveraging the time interval during which a user namespace has been created but a PID namespace has not been created.
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Analysis
by VulDB Data Team • 04/28/2017
The vulnerability described in CVE-2013-1958 represents a critical capability enforcement flaw within the Linux kernel's UNIX domain socket implementation. This issue specifically affects the scm_check_creds function located in net/core/scm.c, which is responsible for validating credentials during socket communication operations. The flaw exists in kernel versions prior to 3.8.6 and demonstrates a significant weakness in the kernel's privilege management system that can be exploited by local attackers to bypass intended access controls.
The technical root cause of this vulnerability lies in the improper handling of capability requirements when processing PID values associated with UNIX domain sockets. During the brief time interval between when a user namespace has been created and before a PID namespace has been established, the kernel fails to properly validate the capabilities of processes attempting to manipulate socket credentials. This temporal window creates an opportunity for malicious processes to exploit the system by crafting specific socket operations that leverage the incomplete namespace setup to escalate privileges or bypass access restrictions.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally undermines the kernel's namespace isolation mechanisms. Local attackers can exploit this flaw to gain unauthorized access to resources that should be restricted to specific user namespaces or PID namespaces. The vulnerability is particularly dangerous because it operates within the kernel's core networking subsystem, meaning that successful exploitation can lead to complete system compromise without requiring external network access or complex attack vectors.
From a cybersecurity perspective, this vulnerability aligns with CWE-284, which addresses improper access control, and demonstrates the importance of proper capability enforcement in kernel space. The attack pattern follows principles outlined in the ATT&CK framework under privilege escalation techniques, specifically targeting kernel-level vulnerabilities to gain elevated system privileges. The flaw represents a classic example of temporal security issues where the system's state during transition periods creates exploitable conditions.
Mitigation strategies for this vulnerability primarily focus on kernel updates and system hardening measures. Organizations should immediately apply the kernel patch released in version 3.8.6 which addresses the capability enforcement issue in the scm_check_creds function. Additionally, system administrators should implement proper monitoring of user namespace creation events and consider implementing additional controls to limit the time intervals during which user namespaces exist without corresponding PID namespaces. The vulnerability also highlights the importance of maintaining current kernel versions and implementing comprehensive security auditing procedures to identify similar temporal security gaps in system components.