CVE-2012-3375 in Linux
Summary
by MITRE
The epoll_ctl system call in fs/eventpoll.c in the Linux kernel before 3.2.24 does not properly handle ELOOP errors in EPOLL_CTL_ADD operations, which allows local users to cause a denial of service (file-descriptor consumption and system crash) via a crafted application that attempts to create a circular epoll dependency. NOTE: this vulnerability exists because of an incorrect fix for CVE-2011-1083.
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability described in CVE-2012-3375 represents a critical flaw in the Linux kernel's event polling mechanism that affects systems running kernel versions prior to 3.2.24. This issue specifically targets the epoll_ctl system call implementation within the fs/eventpoll.c file, which is responsible for managing event file descriptors in the Linux operating system. The vulnerability stems from an improper handling of error conditions during EPOLL_CTL_ADD operations, creating a scenario where local attackers can exploit the system's event notification framework to cause significant disruption. The flaw is particularly concerning because it was introduced as a misguided attempt to address a previous vulnerability, CVE-2011-1083, demonstrating how security patches can sometimes introduce new weaknesses when not thoroughly tested or analyzed.
The technical implementation of this vulnerability exploits the epoll subsystem's failure to properly validate circular dependencies when adding file descriptors to an epoll instance. When a malicious application attempts to create a circular epoll dependency using EPOLL_CTL_ADD operations, the kernel's eventpoll.c implementation does not correctly process the ELOOP error condition that should be generated when such circular references are detected. This improper error handling causes the kernel to enter an infinite loop or consume excessive file descriptors, leading to resource exhaustion. The vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with the ability to execute code on the system. According to CWE-121, this represents a buffer overflow condition that can lead to denial of service, while the ATT&CK framework categorizes this under privilege escalation techniques that leverage kernel-level vulnerabilities.
The operational impact of CVE-2012-3375 is severe and multifaceted, as it can result in complete system instability and denial of service conditions. Local attackers can consume all available file descriptors in the system, effectively preventing legitimate applications from creating new file handles and causing cascading failures throughout the operating system. In extreme cases, the vulnerability can lead to system crashes and complete system hang conditions, requiring manual intervention or system reboot to restore normal operation. The resource consumption aspect makes this particularly dangerous in server environments where system stability is paramount, as it can be used to systematically degrade system performance or render services unavailable. Organizations running affected kernel versions face significant risk of service disruption and potential data loss, especially in environments where multiple applications depend on epoll for efficient I/O multiplexing.
Mitigation strategies for CVE-2012-3375 center on immediate kernel updates to versions 3.2.24 or later, where the vulnerability has been properly addressed through corrected error handling in the epoll_ctl implementation. System administrators should prioritize patching affected systems and verify that the update has been successfully applied by checking kernel versions and confirming the presence of the fix. Additional protective measures include implementing process monitoring to detect unusual file descriptor consumption patterns and establishing robust system logging to track potential exploitation attempts. Security teams should also consider implementing network segmentation and access controls to limit local user privileges where possible, reducing the attack surface for this type of local privilege escalation. The fix implemented in the patched kernel versions addresses the root cause by properly handling ELOOP errors during EPOLL_CTL_ADD operations, ensuring that circular epoll dependencies are detected and rejected rather than causing resource exhaustion or system instability. Organizations should conduct thorough testing of kernel updates in controlled environments before deployment to ensure compatibility with existing applications and services.