CVE-2011-2211 in Linux
Summary
by MITRE
The osf_wait4 function in arch/alpha/kernel/osf_sys.c in the Linux kernel before 2.6.39.4 on the Alpha platform uses an incorrect pointer, which allows local users to gain privileges by writing a certain integer value to kernel memory.
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Analysis
by VulDB Data Team • 12/03/2021
The CVE-2011-2211 vulnerability represents a critical privilege escalation flaw within the Linux kernel's Alpha platform implementation. This issue resides in the osf_wait4 function located in arch/alpha/kernel/osf_sys.c, which handles system calls for waiting on child processes. The vulnerability specifically affects Linux kernel versions prior to 2.6.39.4, making it a longstanding concern that impacted numerous systems running on Alpha architecture. The flaw demonstrates a classic case of improper pointer handling that can be exploited by local attackers to execute arbitrary code with elevated privileges.
The technical root cause of this vulnerability stems from an incorrect pointer usage within the osf_wait4 function that processes operating system function calls on Alpha systems. When a local user executes a specific sequence of operations, the function attempts to write a particular integer value to kernel memory using an improperly validated pointer. This mismanagement allows the attacker to manipulate kernel data structures and potentially overwrite critical memory locations. The vulnerability aligns with CWE-822, which addresses the issue of an uninitialized pointer being used for memory access, and represents a form of memory corruption that can lead to privilege escalation. The flaw essentially creates a pathway for unprivileged users to manipulate kernel memory contents through crafted system call parameters.
The operational impact of CVE-2011-2211 extends beyond simple privilege escalation, as it fundamentally compromises system integrity and security boundaries. A successful exploitation allows local users to gain root privileges, effectively bypassing all kernel-level security mechanisms and access controls. This vulnerability is particularly concerning in multi-user environments where local access might be granted to untrusted users. The attack vector requires only local system access, making it accessible through various means including compromised user accounts, shared systems, or even legitimate administrative access that could be misused. The vulnerability affects systems running on Alpha platform architecture, which includes servers and workstations that may still be operational in legacy environments or specialized applications where Alpha architecture support remains necessary.
Mitigation strategies for CVE-2011-2211 primarily focus on immediate kernel updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 2.6.39.4 or later, which contains the necessary patches to correct the pointer handling error in the osf_wait4 function. System administrators should also implement comprehensive monitoring to detect unusual kernel memory access patterns or unauthorized privilege escalation attempts. Additional defensive measures include restricting local user access where possible, implementing proper system access controls, and maintaining up-to-date security patches across all systems. The vulnerability demonstrates the importance of thorough code review and testing for pointer management in kernel space, as these issues can have severe consequences when exploited. Organizations should also consider the ATT&CK framework's privilege escalation techniques, particularly those related to kernel exploits, to understand how such vulnerabilities might be leveraged in targeted attacks. Given the nature of the flaw, regular security assessments of kernel components and proper input validation mechanisms should be implemented as part of overall system security posture.