CVE-2019-8980 in Linux
Summary
by MITRE
A memory leak in the kernel_read_file function in fs/exec.c in the Linux kernel through 4.20.11 allows attackers to cause a denial of service (memory consumption) by triggering vfs_read failures.
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Analysis
by VulDB Data Team • 07/11/2023
The vulnerability identified as CVE-2019-8980 represents a critical memory management flaw within the Linux kernel that specifically targets the kernel_read_file function located in the fs/exec.c file. This memory leak occurs during the execution of virtual file system read operations and affects all Linux kernel versions up to and including 4.20.11. The flaw stems from inadequate memory cleanup procedures when the virtual file system encounters read failures during kernel execution processes, creating a persistent memory consumption issue that can be exploited by malicious actors.
The technical implementation of this vulnerability involves the kernel's handling of file reading operations within the execution context where the kernel_read_file function fails to properly release allocated memory resources when vfs_read operations encounter errors. This memory leak manifests when the kernel attempts to read files during program execution and subsequently fails to properly deallocate memory that was allocated for these operations, leading to progressive memory exhaustion over time. The vulnerability operates at the kernel level, making it particularly dangerous as it can affect system stability and performance without requiring elevated privileges from the attacker.
From an operational perspective, this vulnerability creates a significant denial of service condition where attackers can systematically consume system memory resources through repeated triggering of the affected code path. The memory consumption occurs gradually but persistently, making it difficult to detect initially while gradually degrading system performance until complete system failure or crash occurs. This type of vulnerability aligns with CWE-401, which describes improper handling of memory allocation and deallocation, and can be categorized under ATT&CK technique T1499.001 for resource exhaustion attacks. The impact extends beyond simple service disruption to potentially compromising the availability of critical system services and applications that depend on stable kernel memory management.
The exploitation of this vulnerability requires minimal privileges and can be executed through normal file system operations that trigger the kernel_read_file function with failing vfs_read calls. System administrators and security professionals should prioritize patching affected kernel versions to address this memory leak, as the vulnerability can be leveraged by both malicious actors and legitimate users who inadvertently trigger the problematic code path. The recommended mitigation strategy involves applying the latest kernel updates from the Linux kernel security team, which contain fixes specifically designed to ensure proper memory deallocation when vfs_read operations fail. Additionally, system monitoring should include tracking memory consumption patterns to detect potential exploitation attempts, and implementing proper kernel hardening measures to reduce the attack surface of the affected system components.