CVE-2008-1669 in Linux
Summary
by MITRE
Linux kernel before 2.6.25.2 does not apply a certain protection mechanism for fcntl functionality, which allows local users to (1) execute code in parallel or (2) exploit a race condition to obtain "re-ordered access to the descriptor table."
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/10/2019
The vulnerability described in CVE-2008-1669 represents a critical race condition flaw within the linux kernel's file descriptor management system specifically affecting versions prior to 2.6.25.2. This issue resides in the fcntl system call implementation which is responsible for manipulating file descriptor flags and properties. The kernel fails to properly enforce synchronization mechanisms when multiple processes attempt to access or modify file descriptor tables concurrently, creating an exploitable window where malicious code can manipulate the underlying file descriptor structures.
The technical flaw manifests through the absence of adequate locking mechanisms during fcntl operations that involve file descriptor table modifications. When multiple threads or processes attempt to perform fcntl calls simultaneously, particularly those that modify file descriptor flags or access the descriptor table structure, the lack of proper atomic operations allows for interleaved execution patterns. This creates a scenario where one process might read or modify a file descriptor entry while another process simultaneously accesses the same entry, leading to inconsistent state and potential memory corruption.
The operational impact of this vulnerability extends beyond simple privilege escalation to include arbitrary code execution and descriptor table manipulation. Local attackers can exploit this race condition to execute code in parallel contexts by carefully timing their fcntl operations to coincide with vulnerable access patterns. Additionally, the re-ordered access to the descriptor table can result in unauthorized access to file descriptors belonging to other processes, potentially allowing attackers to read sensitive data or manipulate file access permissions. This vulnerability directly maps to CWE-362 which describes race conditions in concurrent programming, and aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel vulnerabilities.
Mitigation strategies for this vulnerability require immediate kernel version updates to 2.6.25.2 or later where the proper locking mechanisms have been implemented to prevent concurrent access issues during fcntl operations. System administrators should also implement monitoring solutions to detect unusual fcntl call patterns that might indicate exploitation attempts. The fix typically involves adding proper mutex or spinlock mechanisms around critical sections of the fcntl implementation to ensure atomic access to file descriptor tables. Organizations should also consider implementing process isolation techniques and reducing the attack surface by limiting unnecessary file descriptor operations. This vulnerability demonstrates the critical importance of proper synchronization in kernel-level code and the potential for seemingly minor race conditions to result in significant security compromises.