CVE-1999-0401 in Linux
Summary
by MITRE
A race condition in Linux 2.2.1 allows local users to read arbitrary memory from /proc files.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability identified as CVE-1999-0401 represents a critical race condition flaw discovered in Linux kernel version 2.2.1 that fundamentally compromises system security through improper handling of /proc filesystem access. This vulnerability specifically targets the kernel's implementation of the /proc virtual filesystem which provides an interface to kernel data structures and system information. The race condition occurs during the process of reading memory segments through /proc files, creating a window where concurrent access can lead to unpredictable behavior and information disclosure.
The technical flaw stems from inadequate synchronization mechanisms within the kernel's /proc file handling code. When multiple processes attempt to access the same /proc file simultaneously, the kernel fails to properly serialize these operations, allowing one process to read memory that may have been modified or freed by another concurrent process. This particular race condition manifests in the kernel's memory management subsystem where the timing of memory allocation and deallocation creates opportunities for unauthorized memory access. The vulnerability is classified under CWE-362, which specifically addresses race conditions in software implementations, and aligns with ATT&CK technique T1003.008 related to OS credential dumping through kernel memory access.
The operational impact of this vulnerability extends beyond simple information disclosure, as local users can leverage this race condition to read arbitrary memory locations from the kernel space. This capability enables attackers to extract sensitive information including kernel memory addresses, system credentials, and potentially other confidential data stored in memory. The vulnerability is particularly dangerous because it operates at the kernel level, bypassing typical user-space security controls and access restrictions. Attackers can use this flaw to gain insights into kernel memory layout, potentially leading to more sophisticated attacks such as kernel exploitation or privilege escalation. The race condition makes exploitation somewhat unpredictable but still achievable through careful timing and multiple attempts, as the vulnerability depends on specific timing windows during concurrent process execution.
Mitigation strategies for CVE-1999-0401 primarily involve upgrading to patched kernel versions where the race condition has been resolved through proper synchronization mechanisms and atomic operations. System administrators should immediately implement kernel updates to address this vulnerability, as no reliable workarounds exist for the underlying race condition. The fix typically involves implementing proper mutex locking or other synchronization primitives to ensure that concurrent access to /proc files does not result in memory corruption or unauthorized access. Security monitoring should include detection of suspicious /proc file access patterns and concurrent process behaviors that might indicate exploitation attempts. Additionally, system hardening measures such as restricting local user access to critical system resources and implementing proper access controls for /proc filesystem entries can help reduce the attack surface and limit potential impact of similar vulnerabilities. Organizations should also consider implementing kernel integrity checking mechanisms and regular security audits to identify and address similar race condition vulnerabilities in their systems.