CVE-2016-10729 in Amanda
Summary
by MITRE
An issue was discovered in Amanda 3.3.1. A user with backup privileges can trivially compromise a client installation. The "runtar" setuid root binary does not check for additional arguments supplied after --create, allowing users to manipulate commands and perform command injection as root.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/06/2020
The vulnerability identified as CVE-2016-10729 resides within the Amanda backup software version 3.3.1, specifically affecting the runtar setuid root binary component. This flaw represents a critical privilege escalation vulnerability that allows authenticated users with backup privileges to execute arbitrary commands with root privileges. The issue stems from improper argument validation within the runtar binary, which is designed to operate with elevated privileges to perform backup operations on client systems. The binary's failure to properly sanitize command line arguments creates an exploitable condition that directly violates security principles of least privilege and input validation.
The technical implementation of this vulnerability occurs through the manipulation of command line arguments passed to the runtar binary during backup operations. When users supply additional arguments after the --create flag, the binary fails to validate or sanitize these inputs before executing system commands. This behavior creates a command injection vector that allows attackers to inject malicious commands that get executed with root privileges. The flaw is categorized under CWE-78 as a command injection vulnerability, where the software directly incorporates user-supplied data into system command execution without proper sanitization. The setuid mechanism, intended to provide necessary system privileges for backup operations, becomes a security risk when combined with inadequate input validation.
The operational impact of this vulnerability is severe and far-reaching for organizations using Amanda backup systems. An authenticated user with backup privileges can leverage this flaw to execute arbitrary code as root, potentially leading to complete system compromise. Attackers could use this vulnerability to escalate privileges beyond their initial access level, gain unauthorized access to sensitive data, modify system configurations, install backdoors, or perform other malicious activities that would otherwise require root access. The vulnerability affects the integrity and confidentiality of backup operations, as attackers can manipulate backup processes to exfiltrate data or corrupt backup images. This represents a critical failure in the principle of least privilege, where the backup user's privileges are unnecessarily elevated to root level without proper safeguards.
Mitigation strategies for this vulnerability should focus on immediate patching of the Amanda software to version 3.3.2 or later, which contains the necessary fixes for the argument validation issue. Organizations should also implement additional security controls such as restricting access to the runtar binary and its command line arguments, monitoring for suspicious command execution patterns, and employing principle of least privilege enforcement. The fix typically involves implementing proper argument validation and sanitization within the runtar binary to prevent additional arguments from being processed without proper verification. Security practitioners should also consider implementing network segmentation, access controls, and regular security audits to detect and prevent exploitation attempts. This vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and demonstrates the importance of proper input validation in privileged software components. Organizations should conduct comprehensive vulnerability assessments to identify similar issues in other setuid binaries and implement robust security monitoring to detect potential exploitation attempts.