CVE-2004-0177 in Linux
Summary
by MITRE
The ext3 code in Linux 2.4.x before 2.4.26 does not properly initialize journal descriptor blocks, which causes an information leak in which in-memory data is written to the device for the ext3 file system, which allows privileged users to obtain portions of kernel memory by reading the raw device.
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Analysis
by VulDB Data Team • 05/25/2019
The vulnerability described in CVE-2004-0177 represents a critical information disclosure flaw within the ext3 file system implementation of Linux kernel versions 2.4.x prior to 2.4.26. This issue stems from improper initialization of journal descriptor blocks during the ext3 file system operation, creating a pathway for unauthorized data exposure. The flaw specifically affects the journaling mechanism that ext3 employs to maintain file system consistency and integrity. When journal descriptor blocks are not properly initialized, they retain residual data from previous operations, leading to potential information leakage through the device's raw data access channels.
The technical implementation of this vulnerability involves the kernel's ext3 subsystem failing to adequately clear or reset journal descriptor blocks before reuse. These blocks serve as metadata containers that track file system transactions and maintain journal consistency. When the kernel processes file system operations, it writes journal entries to these blocks, but in affected versions, the initialization process is incomplete or absent entirely. This incomplete initialization means that memory locations previously occupied by sensitive kernel data remain accessible through direct device reads, effectively creating a window for information disclosure attacks. The vulnerability is particularly concerning because it allows privileged users to directly access raw device data, bypassing normal file system access controls and security boundaries that would typically prevent such exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers with privileged access to potentially extract sensitive kernel memory contents. This includes potentially confidential system information, cryptographic keys, or other privileged data that could be used to escalate privileges or conduct further attacks. The vulnerability affects the fundamental integrity of the ext3 file system's journaling mechanism, which is critical for maintaining file system consistency during system crashes or power failures. Attackers could exploit this flaw to gain insights into kernel memory layouts, system configurations, or other sensitive operational details that would normally remain protected within the kernel's memory space.
Mitigation strategies for CVE-2004-0177 primarily focus on upgrading to Linux kernel versions 2.4.26 or later, where the journal descriptor block initialization issue has been properly addressed. System administrators should prioritize patching affected systems and implementing comprehensive monitoring to detect any potential exploitation attempts. The vulnerability aligns with CWE-200, which addresses improper information disclosure, and represents a classic example of how insufficient initialization of system resources can create security vulnerabilities. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and information gathering, as it enables attackers to extract kernel memory contents that could be leveraged for further system compromise. Organizations should also implement proper access controls and monitor for unusual device read patterns that might indicate exploitation attempts, as the vulnerability specifically allows for direct raw device access that bypasses normal file system security mechanisms.