CVE-2011-4915 in Linux
Summary
by MITRE
fs/proc/base.c in the Linux kernel through 3.1 allows local users to obtain sensitive keystroke information via access to /proc/interrupts.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability described in CVE-2011-4915 represents a significant information disclosure issue within the Linux kernel's process management subsystem. This flaw exists in the fs/proc/base.c file and affects kernel versions through 3.1, creating a pathway for local attackers to access sensitive keystroke information through seemingly benign system interfaces. The vulnerability stems from improper access controls within the /proc filesystem, specifically in how interrupt information is exposed to user-space processes, allowing unauthorized access to potentially sensitive data that should remain protected within kernel memory spaces.
The technical implementation of this vulnerability exploits the design of the /proc filesystem interface which provides a virtual filesystem for accessing kernel data structures. In the affected kernel versions, the /proc/interrupts file does not properly enforce access restrictions, enabling local users to read interrupt statistics that may contain information about system activity, including keyboard input events that are processed through interrupt handlers. This occurs because the kernel's process management code fails to adequately separate sensitive interrupt data from general system information, creating a situation where user-space processes can access data that should be restricted to kernel-level operations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable local attackers to gather keystroke information that may include passwords, commands, or other sensitive input data. This represents a direct violation of the principle of least privilege and can potentially lead to privilege escalation or credential compromise if the intercepted keystrokes contain authentication information. The vulnerability affects all local users on the system, making it particularly dangerous in multi-user environments where one compromised account could potentially access information from other users or system processes. According to CWE standards, this maps to CWE-200: Information Exposure and CWE-264: Permissions, Privileges, and Access Controls, as it involves improper access control mechanisms within the kernel.
Mitigation strategies for this vulnerability require immediate kernel updates to versions that address the access control flaw in the /proc filesystem implementation. System administrators should prioritize patching affected systems, as this vulnerability does not require special privileges beyond local user access and can be exploited by any user with shell access to the system. Additionally, organizations should implement monitoring for unusual access patterns to /proc filesystem entries and consider implementing additional access controls through kernel parameters or security modules. The ATT&CK framework categorizes this vulnerability under T1083: File and Directory Discovery and T1056: Input Injection, as it enables discovery of system information and potentially provides a means for capturing user input through system interfaces. Organizations should also consider implementing kernel lockdown mechanisms or other security hardening measures to prevent unauthorized access to kernel memory interfaces and reduce the attack surface for similar information disclosure vulnerabilities.