CVE-2002-1571 in Linux
Summary
by MITRE
The linux 2.4 kernel before 2.4.19 assumes that the fninit instruction clears all registers, which could lead to an information leak on processors that do not clear all relevant SSE registers.
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Analysis
by VulDB Data Team • 09/04/2025
The vulnerability described in CVE-2002-1571 represents a critical flaw in the linux 2.4 kernel version 2.4.19 and earlier, specifically affecting systems utilizing processors with Streaming SIMD Extensions. This issue stems from an incorrect assumption made by the kernel's floating point handling code regarding the behavior of the fninit instruction during processor initialization. The fninit instruction is designed to initialize the x87 floating-point unit and clear its registers, but the kernel code incorrectly assumed it would also clear all SSE registers. This assumption proved erroneous on certain processor implementations where the fninit instruction fails to clear all relevant SSE registers completely.
The technical flaw manifests when the kernel initializes floating point state during context switching or processor initialization phases. When the fninit instruction executes on processors that do not properly clear SSE registers, residual data from previous operations remains in these registers. This residual data can contain sensitive information from previous processes or kernel operations, creating an information leak vulnerability. The flaw is particularly dangerous because it operates at the kernel level and can potentially expose confidential data that should not be accessible to user-space processes or other running applications. This type of information leak can be exploited to gain insights into memory contents, process data, or even cryptographic keys that may have been processed by the floating point unit.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable sophisticated attacks that leverage the leaked information to compromise system security. Attackers could potentially exploit this vulnerability to perform side-channel attacks, where they analyze the leaked data to infer sensitive information about running processes or system state. The vulnerability affects systems running the linux 2.4 kernel series, making it particularly concerning for enterprise environments and servers that may have been running older kernel versions. This issue directly relates to CWE-248, which addresses the improper handling of exceptions and the failure to properly initialize system components, and aligns with ATT&CK technique T1005, which involves data from local system repositories. The vulnerability demonstrates how low-level kernel assumptions can create security weaknesses that affect the entire system, as it operates at the intersection of hardware behavior and software implementation.
The recommended mitigation for CVE-2002-1571 involves upgrading to linux kernel version 2.4.19 or later, where the kernel properly handles the initialization of floating point registers regardless of processor-specific behavior. System administrators should also ensure that all systems running affected kernel versions are updated promptly, as the vulnerability can be exploited by local users or potentially remote attackers depending on the system configuration. Additional mitigations include implementing proper kernel security patches and ensuring that systems are running the latest stable kernel versions. Organizations should also consider monitoring for potential exploitation attempts and implementing proper access controls to limit the impact of any successful exploitation attempts. The vulnerability underscores the importance of thorough testing of kernel code against various processor implementations and the necessity of proper initialization routines that account for hardware-specific behaviors rather than making assumptions about processor capabilities.