CVE-2011-3619 in Linux
Summary
by MITRE
The apparmor_setprocattr function in security/apparmor/lsm.c in the Linux kernel before 3.0 does not properly handle invalid parameters, which allows local users to cause a denial of service (NULL pointer dereference and OOPS) or possibly have unspecified other impact by writing to a /proc/#####/attr/current file.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2011-3619 represents a critical flaw in the Linux kernel's AppArmor security module that affects systems running kernel versions prior to 3.0. This issue resides within the apparmor_setprocattr function located in security/apparmor/lsm.c, where improper parameter validation leads to dangerous system behavior. The vulnerability specifically manifests when local users attempt to write to the /proc/#####/attr/current file, which serves as an interface for managing AppArmor security attributes for processes. This flaw demonstrates a classic lack of input sanitization that can be exploited to disrupt normal system operations.
The technical implementation of this vulnerability stems from insufficient parameter validation within the kernel's security subsystem. When the apparmor_setprocattr function receives malformed or invalid parameters through the proc filesystem interface, it fails to properly validate these inputs before attempting to process them. This leads to a NULL pointer dereference condition that causes the kernel to crash with an OOPS message, effectively rendering the affected system unstable. The improper handling of invalid parameters creates a path where malicious or malformed input can bypass normal kernel safeguards, resulting in kernel-space memory corruption that ultimately terminates the system's ability to function correctly.
From an operational perspective, this vulnerability presents a significant risk to Linux systems as it allows local users to trigger either a denial of service condition or potentially more severe impacts. The denial of service aspect occurs through the NULL pointer dereference that causes kernel panics and system crashes, effectively making the system unavailable to legitimate users. The unspecified other impacts mentioned in the vulnerability description suggest that under certain conditions, this flaw could potentially be leveraged for privilege escalation or other unauthorized system access, though the exact attack vectors remain unclear. The vulnerability is particularly concerning because it affects the core security infrastructure of the Linux kernel, making it a prime target for exploitation in environments where local users have access to system resources.
The impact of CVE-2011-3619 aligns with CWE-20, which describes improper input validation, and represents a direct violation of secure coding practices in kernel space development. This vulnerability demonstrates the critical importance of robust parameter validation in privileged system components, as the failure to validate inputs can lead to catastrophic system failures. From an ATT&CK framework perspective, this vulnerability maps to T1068, which covers 'Exploitation for Privilege Escalation', and T1499, which addresses 'Endpoint Denial of Service', as it enables local users to compromise system availability and potentially gain elevated privileges. The vulnerability's exploitation requires only local access to the system, making it particularly dangerous in multi-user environments where privilege separation is expected but compromised by this kernel flaw.
Mitigation strategies for CVE-2011-3619 primarily involve upgrading to Linux kernel version 3.0 or later, where the vulnerability has been patched through improved parameter validation in the apparmor_setprocattr function. System administrators should also implement additional monitoring to detect unusual activity in the /proc filesystem, particularly around the attr/current interface. While no effective workarounds exist for systems that cannot be immediately upgraded, organizations should consider implementing additional security controls such as restricted user access and monitoring of kernel logs for OOPS messages. The patch for this vulnerability specifically addresses the NULL pointer dereference issue by ensuring that all parameters are properly validated before processing, preventing the kernel from attempting to dereference invalid memory addresses. Security teams should prioritize this vulnerability for remediation, as it represents a fundamental flaw in the kernel's security architecture that could be exploited by malicious users to disrupt system operations or potentially gain unauthorized access to system resources.