CVE-2002-0829 in FreeBSD
Summary
by MITRE
Integer overflow in the Berkeley Fast File System (FFS) in FreeBSD 4.6.1 RELEASE-p4 and earlier allows local users to access arbitrary file contents within FFS to gain privileges by creating a file that is larger than allowed by the virtual memory system.
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Analysis
by VulDB Data Team • 09/06/2019
The vulnerability described in CVE-2002-0829 represents a critical integer overflow flaw within the Berkeley Fast File System implementation in FreeBSD operating systems. This issue affects versions 4.6.1 RELEASE-p4 and earlier, where the file system's handling of file sizes creates a condition that can be exploited by local attackers to bypass normal access controls and escalate privileges. The vulnerability stems from insufficient bounds checking when processing file size parameters, particularly in how the system manages virtual memory allocation for large files.
The technical exploitation occurs when a local user creates a file that exceeds the normal virtual memory limits imposed by the operating system. The integer overflow manifests in the FFS implementation where file size calculations fail to properly validate or constrain the maximum file size that can be allocated. This overflow condition causes the system to misinterpret file size parameters, leading to memory corruption that can be leveraged to access arbitrary file contents. The flaw operates at the kernel level within the file system layer, making it particularly dangerous as it can be exploited without requiring network access or authentication.
From an operational impact perspective, this vulnerability creates a significant privilege escalation vector for local attackers who can manipulate file system operations to gain elevated system privileges. The attack requires only local access to the system, making it particularly concerning for environments where multiple users share the same machine or where unprivileged users have access to system resources. The ability to access arbitrary file contents through this mechanism can potentially expose sensitive system information, configuration files, or other data that should normally be protected from unauthorized access. This vulnerability directly impacts the integrity and confidentiality aspects of the system's security model.
The flaw aligns with CWE-190, which describes integer overflow conditions that can lead to memory corruption and privilege escalation. From an attacker's perspective, this vulnerability maps to techniques described in the ATT&CK framework under privilege escalation tactics, specifically focusing on local privilege escalation through kernel exploits. The vulnerability demonstrates the importance of proper input validation and bounds checking in kernel-level code, as even seemingly benign file system operations can become attack vectors when integer overflows are not properly handled. System administrators should implement immediate mitigation through patching the FreeBSD kernel to versions that address this specific integer overflow condition in the FFS implementation.
The exploitation of this vulnerability requires careful crafting of file size parameters that will trigger the integer overflow condition within the virtual memory subsystem. The attack typically involves creating a file with a size that when processed by the FFS implementation causes the integer to wrap around to a smaller value, allowing the attacker to manipulate memory layouts and potentially access protected file system structures. This type of vulnerability highlights the critical need for comprehensive testing of boundary conditions in kernel code and demonstrates how seemingly minor implementation flaws can have significant security implications for system integrity and access control mechanisms.