CVE-2000-1103 in BSDOS
Summary
by MITRE
rcvtty in BSD 3.0 and 4.0 does not properly drop privileges before executing a script, which allows local attackers to gain privileges by specifying an alternate Trojan horse script on the command line.
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Analysis
by VulDB Data Team • 06/23/2024
The vulnerability described in CVE-2000-1103 affects the rcvtty utility in BSD versions 3.0 and 4.0, representing a critical privilege escalation flaw that exploits improper privilege handling during script execution. This issue stems from the utility's failure to properly drop root privileges before invoking external scripts, creating a pathway for local attackers to execute malicious code with elevated privileges. The vulnerability specifically manifests when rcvtty processes command line arguments that reference script files, allowing adversaries to substitute legitimate scripts with Trojan horse variants that contain malicious payloads.
The technical implementation of this flaw involves the rcvtty utility's privilege management mechanism, which should transition from root to a lower privilege user context before executing any external scripts. However, the implementation contains a critical oversight where privilege dropping occurs after script invocation rather than before it. This timing issue creates a window of opportunity where the utility maintains root privileges during script execution, enabling attackers to manipulate the execution flow through command line parameters. The vulnerability is categorized under CWE-276, which addresses improper privilege management, and aligns with ATT&CK technique T1068, which covers privilege escalation through improper privilege management.
From an operational perspective, this vulnerability poses significant risks to systems running affected BSD versions, as local attackers with minimal privileges can exploit the flaw to gain root access. The attack vector is particularly concerning because it requires only local system access and does not necessitate network connectivity or complex exploitation techniques. Attackers can leverage this vulnerability by placing malicious scripts in locations accessible to rcvtty, then invoking the utility with specific command line arguments that point to these crafted scripts. The impact extends beyond immediate privilege escalation, as successful exploitation provides attackers with complete system control, including the ability to modify system files, install backdoors, or exfiltrate sensitive data.
Mitigation strategies for CVE-2000-1103 should focus on both immediate patching and operational hardening measures. The most effective solution involves applying the appropriate security patches that correct the privilege management implementation in rcvtty to ensure proper privilege dropping before script execution. Organizations should also implement strict file permissions and access controls to prevent unauthorized script modifications, particularly in directories where rcvtty may execute scripts. Additionally, system administrators should conduct regular security audits to identify and remediate similar privilege management flaws in other system utilities, as this vulnerability type represents a common class of security issues in Unix-like operating systems. The remediation process should include monitoring for unauthorized script modifications and implementing automated systems to detect potential privilege escalation attempts.