CVE-2018-14616 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel through 4.17.10. There is a NULL pointer dereference in fscrypt_do_page_crypto() in fs/crypto/crypto.c when operating on a file in a corrupted f2fs image.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2018-14616 represents a critical NULL pointer dereference flaw within the Linux kernel version 4.17.10 and earlier. This issue specifically affects the fscrypt subsystem which handles filesystem encryption operations, particularly when processing files stored on corrupted f2fs (Flash-Friendly File System) images. The flaw manifests during cryptographic operations on encrypted files where the kernel attempts to access a null memory reference, leading to potential system instability and denial of service conditions. The vulnerability exists in the fs/crypto/crypto.c source file within the fscrypt_do_page_crypto() function, which is responsible for performing cryptographic operations on file pages during read and write operations.
The technical exploitation of this vulnerability occurs when the Linux kernel encounters a corrupted f2fs filesystem image containing encrypted files. During normal operation, the fscrypt subsystem initializes cryptographic context structures to handle encryption and decryption of file data. However, in the presence of filesystem corruption, the kernel fails to properly validate the cryptographic context before attempting to dereference it, resulting in a NULL pointer access. This flaw is particularly dangerous because it can be triggered through normal file operations on corrupted filesystems without requiring special privileges or complex attack vectors. The vulnerability is classified under CWE-476 as a NULL pointer dereference, which represents a fundamental programming error where code attempts to access memory through a null pointer reference. The flaw demonstrates poor error handling practices in the kernel's cryptographic subsystem where proper validation of filesystem metadata is not performed before cryptographic operations are initiated.
The operational impact of CVE-2018-14616 extends beyond simple system crashes to potentially compromise the integrity of encrypted file systems and create denial of service conditions for legitimate users. When exploited, this vulnerability can cause kernel panics, system lockups, and forced reboots, effectively rendering affected systems unavailable for normal operations. The vulnerability is particularly concerning for systems that rely heavily on encrypted storage, such as enterprise servers, mobile devices, and systems handling sensitive data. Attackers could potentially leverage this flaw to perform persistent denial of service attacks against systems running vulnerable kernel versions, especially in environments where f2fs filesystems are commonly used. The vulnerability also poses risks to system administrators who may be unaware of filesystem corruption until a crash occurs, potentially leading to data loss or corruption in the process of system recovery. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, as it can be exploited to disrupt system availability without requiring elevated privileges.
Mitigation strategies for CVE-2018-14616 primarily focus on kernel version updates and filesystem management practices. The most effective solution involves upgrading to Linux kernel versions 4.17.11 or later where the vulnerability has been patched through proper validation of cryptographic context structures before dereferencing. System administrators should also implement regular filesystem integrity checks using tools like fsck to identify and repair f2fs filesystem corruption before it can trigger the vulnerability. Additionally, monitoring systems should be configured to detect kernel panics or system crashes that may indicate exploitation attempts. Organizations should also consider implementing filesystem redundancy and backup strategies to minimize the impact of filesystem corruption that could lead to exploitation. The patch for this vulnerability demonstrates proper defensive programming practices by introducing null pointer checks and robust error handling within the cryptographic subsystem, aligning with industry best practices for secure kernel development and preventing similar issues in other cryptographic implementations.