CVE-2013-0871 in Linux
Summary
by MITRE
Race condition in the ptrace functionality in the Linux kernel before 3.7.5 allows local users to gain privileges via a PTRACE_SETREGS ptrace system call in a crafted application, as demonstrated by ptrace_death.
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Analysis
by VulDB Data Team • 05/05/2021
The vulnerability identified as CVE-2013-0871 represents a critical race condition within the Linux kernel's ptrace functionality that existed prior to version 3.7.5. This flaw resides in the kernel's debugging and process tracing mechanisms, specifically affecting how the PTRACE_SETREGS system call handles privilege escalation opportunities. The vulnerability exploits a temporal window during which the kernel fails to properly validate process tracing operations, creating an opportunity for malicious local users to elevate their privileges from standard user level to root access. The issue manifests through crafted applications that leverage the ptrace subsystem to manipulate register states of target processes, ultimately enabling unauthorized privilege elevation.
The technical implementation of this vulnerability stems from insufficient synchronization mechanisms within the kernel's ptrace subsystem. When a process attempts to use PTRACE_SETREGS to modify another process's register state, the kernel must verify that the operation is legitimate and that the requesting process has appropriate permissions. However, due to the race condition, there exists a brief window where these permission checks can be bypassed or circumvented. The vulnerability specifically leverages the interaction between ptrace operations and process privilege management, where the kernel fails to maintain consistent state validation during the critical execution path. This race condition allows an attacker to manipulate the timing of ptrace operations to exploit the kernel's trust model and gain unauthorized access to elevated privileges. The flaw demonstrates a classic example of improper access control mechanisms and inadequate synchronization primitives within kernel space operations.
The operational impact of CVE-2013-0871 is severe and directly affects system integrity and security posture across affected Linux installations. Local users who can execute crafted applications can exploit this vulnerability to gain root privileges without requiring any special permissions or external attack vectors. The vulnerability essentially provides a path for privilege escalation that bypasses normal kernel security mechanisms and access controls. This makes it particularly dangerous in multi-user environments where local access might be available to untrusted users, potentially allowing them to compromise entire systems. The exploit demonstrated through ptrace_death shows how a carefully constructed application can leverage this race condition to manipulate kernel state and elevate privileges. The impact extends beyond individual system compromise, as successful exploitation can lead to complete system control, data exfiltration, and potential lateral movement within networked environments where such systems reside.
Mitigation strategies for CVE-2013-0871 primarily involve applying the appropriate kernel security patches released by the Linux kernel development team. System administrators should immediately update their kernels to version 3.7.5 or later, which contains the necessary fixes for the race condition in ptrace functionality. Additionally, organizations should implement process monitoring and anomaly detection to identify potential exploitation attempts through ptrace operations. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and relates to ATT&CK technique T1068, which covers privilege escalation through local exploitation. Network segmentation and least privilege principles should be enforced to limit the potential impact of successful exploitation, while regular security audits should monitor for unauthorized ptrace usage patterns. System hardening measures including disabling unnecessary ptrace capabilities for non-privileged users and implementing mandatory access controls can further reduce the attack surface. The vulnerability also highlights the importance of kernel security reviews and proper synchronization mechanisms in preventing temporal race conditions that can lead to privilege escalation exploits.