CVE-2004-0138 in Linux
Summary
by MITRE
The ELF loader in Linux kernel 2.4 before 2.4.25 allows local users to cause a denial of service (crash) via a crafted ELF file with an interpreter with an invalid arch (architecture), which triggers a BUG() when an invalid VMA is unmapped.
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Analysis
by VulDB Data Team • 09/02/2019
The vulnerability described in CVE-2004-0138 represents a critical flaw in the Linux kernel's ELF (Executable and Linkable Format) loader implementation that existed in kernel versions prior to 2.4.25. This issue specifically targets the handling of executable files with malformed interpreter sections, creating a condition where the kernel's memory management subsystem fails to properly validate architecture specifications during the loading process. The flaw occurs when a local attacker crafts an ELF file containing an interpreter section with an invalid architecture identifier, which then triggers an unexpected kernel state that leads to system instability.
The technical root cause of this vulnerability lies in the kernel's improper validation of architecture identifiers within ELF interpreter sections during the loading process. When the kernel encounters an ELF file with an invalid arch field in its interpreter segment, the ELF loader fails to properly handle the malformed data structure, resulting in a situation where an invalid virtual memory area (VMA) is created and subsequently attempted to be unmapped. This scenario triggers a BUG() macro within the kernel code, which is designed to indicate critical internal errors and typically results in immediate system termination or crash. The vulnerability specifically affects the kernel's memory management subsystem and represents a classic case of improper input validation combined with inadequate error handling.
The operational impact of CVE-2004-0138 is significant as it enables local privilege escalation to a denial of service condition that can completely crash the target system. Since the vulnerability requires only local access to execute, it can be exploited by any user with access to the system, making it particularly dangerous in multi-user environments. The crash occurs during the ELF loading process, which means that any application or script attempting to execute a maliciously crafted ELF file will trigger the vulnerability, potentially affecting system stability and availability. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, as the kernel fails to properly validate the architecture field before attempting to process it, and aligns with ATT&CK technique T1499.004 for Denial of Service through kernel-level exploitation.
Mitigation strategies for this vulnerability require immediate kernel updates to version 2.4.25 or later, where the issue has been properly addressed through enhanced validation of architecture identifiers in ELF interpreter sections. System administrators should prioritize patching affected systems and implement monitoring for suspicious ELF file execution patterns that might indicate exploitation attempts. Additionally, the vulnerability highlights the importance of proper input validation in kernel space code, where all external data must be rigorously validated before processing to prevent similar issues. The fix implemented in the patched kernel versions involves enhanced checks within the ELF loader to properly validate architecture identifiers and prevent invalid VMAs from being created in the first place. Organizations should also consider implementing file integrity monitoring solutions to detect and prevent the execution of potentially malicious ELF files, particularly in environments where untrusted users have access to system resources.