CVE-2013-4312 in Linux
Summary
by MITRE
The Linux kernel before 4.4.1 allows local users to bypass file-descriptor limits and cause a denial of service (memory consumption) by sending each descriptor over a UNIX socket before closing it, related to net/unix/af_unix.c and net/unix/garbage.c.
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Analysis
by VulDB Data Team • 07/07/2022
The vulnerability identified as CVE-2013-4312 represents a significant flaw in the Linux kernel's handling of Unix domain socket file descriptors that can be exploited to cause resource exhaustion and denial of service conditions. This issue affects Linux kernel versions prior to 4.4.1 and stems from improper management of file descriptor references within the Unix domain socket implementation. The vulnerability specifically resides in the net/unix/af_unix.c and net/unix/garbage.c source files, which govern the functionality and cleanup processes for Unix domain sockets. The flaw allows malicious local users to circumvent normal file descriptor limits by repeatedly sending file descriptors over Unix sockets without proper cleanup, leading to accumulation of references in kernel memory structures.
The technical nature of this vulnerability involves a race condition and reference counting mechanism failure within the kernel's Unix socket subsystem. When file descriptors are sent over Unix sockets, the kernel maintains reference counts to track how many times each descriptor is being used. The vulnerability occurs because the kernel does not properly decrement these reference counts when descriptors are received and processed, allowing for a buildup of references even after the original file descriptors have been closed. This creates a memory leak scenario where kernel memory continues to be allocated for tracking these unreleased references, eventually consuming system resources and leading to system instability or complete denial of service conditions.
From an operational perspective, this vulnerability poses a serious threat to systems running affected kernel versions as it can be exploited by any local user with access to the system. The impact extends beyond simple resource exhaustion to potentially compromise system availability and stability, particularly in environments where Unix domain sockets are heavily utilized for inter-process communication. Attackers can leverage this vulnerability to consume memory resources progressively, making the system unresponsive to legitimate users and applications. The vulnerability is particularly dangerous in server environments where multiple processes communicate through Unix sockets, as the memory consumption can occur gradually but steadily, making detection difficult until the system becomes critically unstable.
The exploitation of this vulnerability aligns with several ATT&CK techniques including privilege escalation through resource exhaustion and denial of service attacks. It also relates to CWE-404, which describes improper resource management, and CWE-362, which covers concurrent execution using shared resources. Organizations should prioritize applying kernel updates to versions 4.4.1 and later, as these releases contain the necessary patches to address the reference counting issues in the Unix socket implementation. System administrators should also consider implementing monitoring solutions to detect unusual memory consumption patterns that might indicate exploitation attempts, while maintaining regular kernel update schedules to prevent similar vulnerabilities from being exploited in the future.