CVE-1999-1517 in FreeBSD
Summary
by MITRE
runtar in the Amanda backup system used in various UNIX operating systems executes tar with root privileges, which allows a user to overwrite or read arbitrary files by providing the target files to runtar.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-1517 represents a critical privilege escalation issue within the Amanda backup system, a widely deployed backup solution for unix operating systems. This flaw exists in the runtar component which serves as a wrapper for the tar command during backup operations. The vulnerability stems from the design decision to execute tar with root privileges, a common pattern in backup systems that assumes all backup operations require elevated permissions. However, this approach creates a dangerous attack surface when user input is not properly sanitized or validated. The specific technical flaw lies in how runtar processes user-provided file paths and archive specifications, allowing malicious users to manipulate the backup process to target arbitrary system files rather than just the intended backup destinations.
The operational impact of this vulnerability extends far beyond simple file access violations, as it enables attackers to perform privilege escalation attacks that can compromise entire system integrity. When a user can manipulate runtar to overwrite arbitrary files, they gain the ability to modify critical system files, configuration data, or even replace executables with malicious versions. This vulnerability directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The attack vector typically involves supplying specially crafted file paths or archive specifications that bypass normal access controls, allowing an attacker to target files outside of the intended backup scope. This represents a fundamental flaw in the principle of least privilege, where the backup system unnecessarily grants root privileges for operations that could be performed with reduced permissions.
From a cybersecurity perspective, this vulnerability demonstrates the dangers of over-privileged backup processes and the importance of proper input validation. The attack can be executed by any user with access to the Amanda system, making it particularly dangerous in multi-user environments where system administrators may not properly monitor or restrict backup access. The vulnerability also aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1566, which covers 'Phishing for Information'. Organizations using Amanda systems would have been particularly vulnerable to this attack as it could be exploited to gain root access to systems without requiring additional authentication or specialized attack tools. The remediation approach involves either restricting runtar to execute with reduced privileges when possible, implementing strict input validation and sanitization of user-provided file paths, or redesigning the backup architecture to avoid the need for root privileges during backup operations. Additionally, organizations should implement proper access controls and monitoring to detect unauthorized backup activities that might indicate exploitation attempts.
The broader implications of this vulnerability highlight the critical need for security reviews of backup systems and the importance of understanding the privilege model used by system components. This flaw serves as a classic example of why security-by-design principles should be applied to all system components, particularly those handling sensitive data or requiring elevated privileges. Modern backup solutions have evolved to address these concerns through improved privilege separation, better input validation, and more granular access controls that prevent such widespread privilege escalation opportunities. Organizations that have not updated their Amanda installations or migrated to more secure backup solutions remain at risk from this and similar historical vulnerabilities that continue to affect legacy systems in production environments.