CVE-2004-0109 in Linux
Summary
by MITRE
Buffer overflow in the ISO9660 file system component for Linux kernel 2.4.x, 2.5.x and 2.6.x, allows local users with physical access to overflow kernel memory and execute arbitrary code via a malformed CD containing a long symbolic link entry.
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Analysis
by VulDB Data Team • 06/28/2019
The vulnerability described in CVE-2004-0109 represents a critical buffer overflow condition within the Linux kernel's ISO9660 file system implementation that affects multiple kernel versions including 2.4.x, 2.5.x, and 2.6.x series. This flaw specifically targets the handling of symbolic link entries within ISO9660 formatted CD-ROM images, creating a pathway for privilege escalation and arbitrary code execution. The vulnerability is particularly concerning because it can be exploited by local users who possess physical access to the target system, eliminating the need for network-based attack vectors or sophisticated remote exploitation techniques. The attack scenario involves crafting a malformed CD image containing an excessively long symbolic link entry that, when mounted by the vulnerable kernel, triggers the buffer overflow condition in kernel memory space.
The technical implementation of this vulnerability stems from inadequate input validation within the ISO9660 file system driver where the kernel fails to properly bounds-check the length of symbolic link entries during file system parsing operations. When the kernel encounters a symbolic link entry that exceeds predetermined buffer limits, the overflow occurs in kernel memory, potentially overwriting adjacent memory structures including function return addresses, control flags, and other critical kernel data. This type of flaw directly maps to CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which encompasses out-of-bounds read vulnerabilities that can lead to memory corruption. The vulnerability operates at the kernel level where the privilege separation between user space and kernel space breaks down, allowing attackers to execute malicious code with kernel privileges.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with complete system compromise capabilities when physical access is available. An attacker with access to a target system can insert a specially crafted CD containing the malformed symbolic link entry, mount the CD, and trigger the overflow condition to gain kernel-level privileges. This attack vector aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically shell code execution, and T1068 for exploit for privilege escalation. The vulnerability's exploitability is enhanced by the fact that it requires no network connectivity or complex attack chaining, making it particularly dangerous in environments where physical security controls are inadequate or compromised.
Mitigation strategies for this vulnerability must address both the immediate kernel-level fix and broader system security practices. The primary remediation involves applying kernel patches that implement proper bounds checking for symbolic link entries within ISO9660 file systems, ensuring that buffer sizes are adequately validated before memory operations occur. System administrators should also implement physical security controls to prevent unauthorized CD insertion, as the vulnerability requires physical access to the target system. Additional protective measures include disabling unnecessary CD-ROM mounting capabilities, implementing strict file system access controls, and monitoring for suspicious mounting activities. Organizations should also consider implementing automated patch management systems to ensure timely application of security updates across all affected kernel versions, as this vulnerability affects multiple kernel releases and requires coordinated remediation efforts across different system configurations.