CVE-2004-0099 in FreeBSD
Summary
by MITRE
mksnap_ffs in FreeBSD 5.1 and 5.2 only sets the snapshot flag when creating a snapshot for a file system, which causes default values for other flags to be used, possibly disabling security-critical settings and allowing a local user to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 09/02/2019
The vulnerability described in CVE-2004-0099 represents a critical flaw in the FreeBSD operating system's snapshot creation mechanism that directly impacts file system security controls. This issue affects FreeBSD versions 5.1 and 5.2 specifically, where the mksnap_ffs utility fails to properly initialize all file system flags during snapshot creation processes. The technical implementation flaw occurs at the kernel level within the file system management subsystem, specifically when the snapshot flag is set without properly configuring the complete set of file system attributes that govern access control and security policies.
The core technical issue stems from improper flag handling within the mksnap_ffs utility which is responsible for creating file system snapshots in FreeBSD's UFS (Unix File System) implementation. When a snapshot is created, the utility correctly sets the snapshot flag but neglects to initialize other critical file system flags that control security-sensitive attributes. This incomplete flag initialization results in the snapshot inheriting default values for these security-critical parameters instead of maintaining the original file system's security configuration. The flaw creates a scenario where file system access controls, permissions, and security policies that were explicitly configured by system administrators are effectively overridden or disabled during the snapshot creation process.
The operational impact of this vulnerability is significant for local users who can exploit this weakness to bypass intended access restrictions and gain unauthorized privileges. Attackers can leverage this vulnerability to create snapshots that inherit default security settings rather than the original restrictive configurations, potentially allowing them to access files or directories that should otherwise be protected. This represents a direct violation of the principle of least privilege and can enable privilege escalation attacks, where local users can manipulate file system security controls to gain elevated access rights. The vulnerability particularly affects environments where strict access controls and security policies are implemented, as the snapshot mechanism becomes a potential attack vector for bypassing these protections.
This vulnerability maps to CWE-254 in the Common Weakness Enumeration, specifically addressing weaknesses in the implementation of security features where security-relevant attributes are not properly initialized or handled. The flaw demonstrates poor input validation and initialization practices in security-critical system components, making it susceptible to exploitation by malicious local users. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as privilege escalation and defense evasion, as it allows attackers to bypass security controls and maintain persistent access to system resources. The vulnerability also relates to privilege abuse techniques where system utilities that should maintain security policies are misconfigured during routine operations.
Mitigation strategies for this vulnerability require immediate patching of affected FreeBSD systems to versions that properly initialize all file system flags during snapshot creation. System administrators should implement monitoring procedures to detect unauthorized snapshot creation activities and verify that security policies are maintained across all file system operations. Additionally, organizations should conduct regular security audits to ensure that file system snapshots maintain the same security attributes as the original file systems, particularly focusing on access control lists, permissions, and security policy enforcement mechanisms. The recommended approach includes updating to patched versions of FreeBSD 5.1 and 5.2, implementing proper file system monitoring, and establishing security baseline verification procedures to prevent similar flag initialization issues in other system components.