CVE-2000-0534 in apsfilter
Summary
by MITRE
The apsfilter software in the FreeBSD ports package does not properly read user filter configurations, which allows local users to execute commands as the lpd user.
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Analysis
by VulDB Data Team • 05/10/2019
The apsfilter software within the FreeBSD ports collection presents a critical privilege escalation vulnerability that stems from improper handling of user filter configurations. This flaw exists in the way the software processes configuration files and user input, creating a path for local attackers to execute arbitrary commands with elevated privileges. The vulnerability specifically targets the lpd user context, which typically operates with higher system privileges than regular users, making this a significant security concern for FreeBSD systems running affected versions of the apsfilter package.
The technical implementation of this vulnerability resides in the insecure parsing and execution mechanisms within the apsfilter configuration handling code. When users configure filter settings through the apsfilter interface, the software fails to properly sanitize or validate the input parameters before processing them. This insufficient input validation creates a command injection vector where maliciously crafted configuration values can be interpreted and executed by the underlying system processes. The flaw operates at the level of configuration file parsing where user-supplied data is directly incorporated into system commands without adequate security checks or sanitization measures.
From an operational standpoint, this vulnerability enables local users to escalate their privileges from standard user accounts to the lpd user account, which typically possesses administrative capabilities within the printing subsystem. This privilege escalation allows attackers to manipulate print jobs, modify system configuration files, access sensitive data, and potentially establish persistent access to the compromised system. The impact extends beyond simple command execution as the lpd user context often has access to system resources and network services that can be leveraged for further attacks within the network infrastructure. This vulnerability particularly affects systems where multiple users share the same machine and where print services are actively utilized.
Mitigation strategies for this vulnerability should focus on immediate patching of the apsfilter package to the latest secure versions that address the configuration parsing flaws. System administrators should also implement proper input validation and sanitization measures within their print management configurations, ensuring that user inputs are properly escaped or filtered before being processed. Additionally, privilege separation techniques should be enforced to minimize the impact of potential exploitation, and regular security audits should be conducted to identify similar vulnerabilities in other system components. Organizations should consider implementing the principle of least privilege for print service accounts and monitor system logs for suspicious activities related to print job processing and configuration changes. This vulnerability aligns with CWE-78 which addresses improper neutralization of special elements used in OS commands, and relates to attack techniques in the MITRE ATT&CK framework under privilege escalation and command execution tactics. The remediation efforts should also include comprehensive security training for system administrators to recognize and prevent similar input validation issues in custom applications and scripts.