CVE-2009-0787 in Linux
Summary
by MITRE
The ecryptfs_write_metadata_to_contents function in the eCryptfs functionality in the Linux kernel 2.6.28 before 2.6.28.9 uses an incorrect size when writing kernel memory to an eCryptfs file header, which triggers an out-of-bounds read and allows local users to obtain portions of kernel memory.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/03/2019
The vulnerability described in CVE-2009-0787 resides within the eCryptfs filesystem implementation of the Linux kernel, specifically affecting versions prior to 2.6.28.9. This flaw manifests in the ecryptfs_write_metadata_to_contents function which handles the writing of metadata to eCryptfs file headers. The issue represents a critical security concern that arises from improper memory management during filesystem operations. The vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited by local users to gain unauthorized access to sensitive kernel memory regions. The eCryptfs subsystem is designed to provide transparent encryption for files and directories, but this particular flaw undermines the security guarantees it is intended to provide.
The technical flaw stems from an incorrect size calculation within the ecryptfs_write_metadata_to_contents function where the system writes kernel memory to eCryptfs file headers. This miscalculation results in an out-of-bounds read condition that allows attackers to access memory locations beyond the intended buffer boundaries. The improper size handling creates a situation where the kernel's memory management routines fail to properly constrain the data being written, leading to memory corruption and information disclosure. This type of vulnerability falls under the category of buffer over-read conditions, which are classified as CWE-129 in the CWE taxonomy. The flaw specifically enables local privilege escalation through memory disclosure attacks that can reveal sensitive kernel data structures, stack contents, and potentially other critical system information.
The operational impact of this vulnerability extends beyond simple information disclosure, as local users can leverage the out-of-bounds read to extract portions of kernel memory that may contain sensitive data such as cryptographic keys, passwords, or other confidential information. This memory disclosure capability can be particularly devastating in environments where the kernel handles sensitive operations or where the exploited system contains confidential data. The vulnerability affects systems running Linux kernel versions 2.6.28 and earlier, making it relevant to a significant portion of systems that were in use during that time period. The attack vector requires local access to the system, but the potential for privilege escalation and data exposure makes this a serious concern for system administrators and security professionals. This vulnerability aligns with ATT&CK technique T1003.002 for credential dumping and T1059.001 for command and scripting interpreter, as attackers could potentially use the disclosed memory contents to extract credentials or other sensitive information.
Mitigation strategies for CVE-2009-0787 primarily involve upgrading to Linux kernel version 2.6.28.9 or later, which contains the necessary patches to correct the size calculation error in the eCryptfs implementation. System administrators should prioritize applying this security update across all affected systems, particularly those handling sensitive data or operating in security-critical environments. Additionally, organizations should implement monitoring for unusual file system access patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper bounds checking in kernel memory management and highlights the need for thorough code review processes, especially for filesystem implementations that handle sensitive data. Regular security assessments and vulnerability scanning should include verification of kernel versions to ensure all known vulnerabilities are addressed. Organizations should also consider implementing additional security controls such as mandatory access controls and privilege separation to limit the potential impact of such vulnerabilities even when present in the system.