CVE-2007-0267 in FreeBSD
Summary
by MITRE
The ufs_lookup function in the Mac OS X 10.4.8 and FreeBSD 6.1 kernels allows local users to cause a denial of service (kernel panic) and possibly corrupt other filesystems by mounting a crafted UNIX File System (UFS) DMG image that contains a corrupted directory entry (struct direct), related to the ufs_dirbad function. NOTE: a third party states that the FreeBSD issue does not cross privilege boundaries.
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Analysis
by VulDB Data Team • 03/08/2025
The vulnerability identified as CVE-2007-0267 represents a critical kernel-level flaw affecting both Mac OS X 10.4.8 and FreeBSD 6.1 operating systems. This issue resides within the ufs_lookup function that handles directory traversal operations in the UFS filesystem implementation. The vulnerability manifests when a local attacker mounts a specially crafted UFS DMG image containing malformed directory entries, specifically struct direct structures that violate expected filesystem formatting conventions. The flaw operates at the kernel level, making it particularly dangerous as it can trigger system instability and potentially compromise the integrity of other filesystems on the same system.
The technical root cause of this vulnerability stems from inadequate input validation within the ufs_dirbad function, which is responsible for handling corrupted directory entries during filesystem operations. When the ufs_lookup function processes a malformed directory entry, it fails to properly validate the structure of the directory data before attempting to access or interpret the corrupted information. This lack of proper boundary checking and validation allows maliciously constructed directory entries to cause the kernel to attempt invalid memory operations or access corrupted data structures. The vulnerability specifically targets the struct direct data structure which contains directory entry information including filenames, inode numbers, and entry types, and when these fields contain unexpected values, the kernel's directory traversal logic becomes unstable.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise system stability and data integrity. Local attackers can trigger kernel panics that result in complete system crashes, forcing users to reboot their systems and potentially causing data loss if filesystems were in the middle of transactions. The described behavior suggests that the vulnerability may not only cause immediate system instability but could also lead to filesystem corruption in adjacent volumes or partitions, as the kernel panic might propagate memory corruption across different filesystem contexts. This cross-contamination risk makes the vulnerability particularly concerning in multi-filesystem environments where system stability depends on proper isolation between different storage volumes.
From a cybersecurity perspective, this vulnerability aligns with CWE-125, which addresses out-of-bounds read conditions in software implementations. The flaw represents a classic example of insufficient input validation and boundary checking in kernel code, making it susceptible to exploitation through crafted data inputs. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service tactics, as local users can leverage it to disrupt system operations without requiring elevated privileges. The fact that the FreeBSD implementation does not cross privilege boundaries suggests that while the vulnerability affects the kernel directly, it may not provide a direct path to privilege escalation in that specific implementation. However, the potential for filesystem corruption and system instability makes it a significant concern for system administrators who must maintain availability and data integrity across their computing environments.
Mitigation strategies for CVE-2007-0267 should focus on immediate patching of affected systems, as the vulnerability is specifically addressed through kernel updates that improve input validation in the ufs_lookup and ufs_dirbad functions. System administrators should implement strict filesystem validation policies and avoid mounting untrusted UFS images from unknown sources. The vulnerability highlights the importance of maintaining updated kernel versions and implementing proper filesystem monitoring to detect potentially malicious or corrupted image files. Additionally, organizations should consider implementing automated patch management systems to ensure timely deployment of security updates and reduce the window of exposure to such kernel-level vulnerabilities that can compromise system stability and data integrity.