CVE-2011-1019 in Linux
Summary
by MITRE
The dev_load function in net/core/dev.c in the Linux kernel before 2.6.38 allows local users to bypass an intended CAP_SYS_MODULE capability requirement and load arbitrary modules by leveraging the CAP_NET_ADMIN capability.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability identified as CVE-2011-1019 represents a significant privilege escalation flaw within the Linux kernel's module loading mechanism. This issue affects the net/core/dev.c file in kernel versions prior to 2.6.38 and demonstrates how insufficient capability checks can lead to unauthorized module loading. The flaw specifically resides in the dev_load function which is responsible for handling network device loading operations. Under normal circumstances, the kernel enforces strict capability requirements to prevent unauthorized module loading, particularly for the CAP_SYS_MODULE capability which is essential for loading kernel modules. However, this vulnerability creates an exploitable path where local users can bypass the intended security controls through a misconfiguration in capability validation.
The technical implementation of this vulnerability stems from a flawed capability check within the kernel's network device loading subsystem. When a user attempts to load a network device module, the kernel should verify that the user possesses the appropriate privileges, specifically requiring CAP_SYS_MODULE capability for module loading operations. The vulnerability occurs because the dev_load function fails to properly validate this requirement when the user has CAP_NET_ADMIN capability, which is typically granted to network administrators for network device management tasks. This oversight creates a privilege escalation path where a user with network administration privileges can leverage their existing capabilities to load arbitrary kernel modules without proper authorization. The flaw essentially allows a local attacker to bypass the kernel's module loading security controls by exploiting the relationship between different capability sets.
The operational impact of CVE-2011-1019 is substantial as it provides local users with the ability to load arbitrary kernel modules, potentially leading to complete system compromise. This vulnerability enables attackers to load malicious kernel modules that could perform various malicious activities including privilege escalation, data exfiltration, or system monitoring. The implications extend beyond simple privilege escalation since kernel modules operate at the highest privilege level within the kernel space, giving attackers complete control over the system. This capability allows for persistent backdoor installation, rootkit deployment, and the ability to hide malicious activities from normal system monitoring. The vulnerability affects any local user who possesses CAP_NET_ADMIN capability, which is commonly granted to network administrators, system operators, or users running network management applications. The attack vector is particularly concerning because it requires minimal privileges and can be exploited from within the system, making it difficult to detect and prevent.
The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and represents a clear example of insufficient privilege checking within kernel space operations. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques where adversaries leverage existing permissions to gain higher privileges. The flaw demonstrates how capability-based security models can be undermined when implementation details fail to enforce proper access controls. Organizations should implement immediate mitigations including kernel updates to version 2.6.38 or later where the vulnerability has been patched. System administrators should also review and minimize the assignment of CAP_NET_ADMIN capability to users who do not require it for their operational tasks. Additionally, monitoring for unusual module loading activities and implementing kernel module signing policies can help detect exploitation attempts. The vulnerability underscores the critical importance of proper capability validation in kernel space operations and the necessity of maintaining up-to-date system configurations to prevent unauthorized module loading operations.