CVE-2014-7822 in Linux
Summary
by MITRE
The implementation of certain splice_write file operations in the Linux kernel before 3.16 does not enforce a restriction on the maximum size of a single file, which allows local users to cause a denial of service (system crash) or possibly have unspecified other impact via a crafted splice system call, as demonstrated by use of a file descriptor associated with an ext4 filesystem.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability described in CVE-2014-7822 represents a critical flaw in the Linux kernel's handling of file operations, specifically within the splice_write implementation that affects systems running kernel versions prior to 3.16. This issue manifests in the improper enforcement of maximum file size restrictions during splice system calls, creating a potential vector for both denial of service attacks and unspecified security implications. The vulnerability is particularly concerning because it operates at the kernel level, where malicious actions can have far-reaching consequences for system stability and security.
The technical flaw resides in how the kernel processes splice_write operations when dealing with file descriptors associated with ext4 filesystems. The splice system call is designed to move data between file descriptors without requiring intermediate buffers, making it an efficient method for data transfer. However, the implementation fails to properly validate or enforce size limitations on individual file operations, allowing an attacker to craft malicious splice calls that can manipulate file sizes beyond normal constraints. This lack of proper size validation creates a condition where the kernel's internal data structures can become corrupted or exhausted, leading to system instability. The vulnerability operates under CWE-126 which specifically addresses "Buffer Over-read" conditions, where the kernel attempts to access memory beyond allocated boundaries during file size operations.
The operational impact of this vulnerability extends beyond simple system crashes, as local users with access to the system can exploit this weakness to cause significant disruption. The denial of service aspect can result in complete system crashes requiring manual reboot, while the unspecified other impacts could potentially include privilege escalation or data corruption. Attackers can leverage this vulnerability by creating malicious file descriptors and executing crafted splice operations that manipulate file sizes in ways that exhaust kernel memory or corrupt internal file system structures. The attack surface is particularly broad since splice operations are commonly used in various system functions and applications, making it difficult to prevent without kernel-level patches.
Mitigation strategies for CVE-2014-7822 primarily focus on immediate kernel updates to versions 3.16 or later where the vulnerability has been addressed through proper enforcement of file size restrictions. System administrators should prioritize patching affected systems, particularly those running older kernel versions that remain in production environments. Additional protective measures include implementing strict file system access controls and monitoring for unusual splice operations that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 which covers "Command and Scripting Interpreter: PowerShell," as attackers may use scripting to automate the exploitation of such kernel-level vulnerabilities. Organizations should also consider implementing kernel hardening measures and regular security audits to identify potential exploitation vectors. Given the nature of the vulnerability, regular kernel updates and security monitoring remain the most effective long-term solutions to prevent both exploitation and system compromise.