CVE-2004-0435 in FreeBSD
Summary
by MITRE
Certain "programming errors" in the msync system call for FreeBSD 5.2.1 and earlier, and 4.10 and earlier, do not properly handle the MS_INVALIDATE operation, which leads to cache consistency problems that allow a local user to prevent certain changes to files from being committed to disk.
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Analysis
by VulDB Data Team • 06/28/2019
The vulnerability described in CVE-2004-0435 represents a critical flaw in the FreeBSD operating system's memory management subsystem, specifically within the msync system call implementation. This issue affects FreeBSD versions 5.2.1 and earlier, as well as version 4.10 and earlier, making it a significant concern for systems running these older releases. The vulnerability stems from improper handling of the MS_INVALIDATE operation flag within the msync system call, which is responsible for synchronizing memory-mapped regions with their underlying storage.
The technical flaw manifests when the msync system call processes memory mappings with the MS_INVALIDATE flag, which should invalidate cached copies of data in memory that corresponds to the specified file region. However, due to programming errors in the implementation, the system fails to properly invalidate these cache entries, leading to inconsistent states between memory and disk storage. This cache inconsistency creates a scenario where modifications to files may not be properly committed to persistent storage, effectively allowing data to remain in memory without being written to disk.
From an operational perspective, this vulnerability enables local users to exploit cache consistency problems to prevent certain file changes from being committed to disk storage. The impact extends beyond simple data loss, as it can lead to data corruption, incomplete file writes, and potential system instability. Attackers can leverage this flaw to maintain persistence by ensuring that their modifications to files remain in memory rather than being written to disk, effectively creating a form of data tampering that bypasses normal file system integrity mechanisms. This represents a significant concern for systems where data integrity is paramount, as it undermines the fundamental assumption that file modifications will be properly synchronized with storage.
The vulnerability aligns with CWE-119, which describes weaknesses in memory handling, and demonstrates how improper memory management can lead to serious security implications. From an ATT&CK framework perspective, this vulnerability could be categorized under privilege escalation and persistence techniques, as local users can exploit it to maintain control over file system modifications without proper audit trails. The flaw essentially creates a backdoor mechanism where file system changes can be silently suppressed, allowing attackers to maintain access while avoiding detection through normal file system monitoring.
Mitigation strategies should focus on immediate system updates to patched versions of FreeBSD that address the msync implementation errors. Organizations should implement comprehensive patch management processes to ensure all affected systems receive updates promptly. Additionally, monitoring systems should be enhanced to detect unusual patterns in file system synchronization behavior, particularly around memory-mapped file operations. System administrators should also consider implementing additional file integrity checking mechanisms and regular audits of file system consistency to detect potential exploitation of this vulnerability. The remediation process must include thorough testing of updated systems to ensure that the patch does not introduce compatibility issues with existing applications that rely on memory mapping functionality.