CVE-2001-0196 in FreeBSD
Summary
by MITRE
inetd ident server in FreeBSD 4.x and earlier does not properly set group permissions, which allows remote attackers to read the first 16 bytes of files that are accessible by the wheel group.
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Analysis
by VulDB Data Team • 02/13/2017
The vulnerability identified as CVE-2001-0196 affects the inetd ident server implementation in FreeBSD versions 4.x and earlier, representing a significant privilege escalation and information disclosure weakness. This flaw resides in the fundamental network service management infrastructure where the ident server process fails to properly enforce group-based file access controls. The issue stems from improper permission handling within the inetd service framework, specifically when processing ident requests from remote clients. When the ident server operates, it does not correctly validate or restrict group permissions, creating an unintended access path that allows remote attackers to retrieve the first 16 bytes of files accessible to the wheel group, which typically contains system administrators and privileged users. This vulnerability operates at the intersection of Unix file permission models and network service security, exploiting the gap between expected and actual privilege enforcement mechanisms.
The technical implementation of this vulnerability involves the inetd daemon's ident server component failing to properly manage the effective group ID when processing incoming ident requests. The flaw manifests when the ident service attempts to access or read file contents on behalf of remote clients, without adequately validating the group membership of the requesting process. This misconfiguration allows attackers to leverage the service's elevated privileges to access restricted file contents, particularly those belonging to the wheel group which traditionally holds administrative privileges. The vulnerability specifically targets the first 16 bytes of accessible files, suggesting that the flaw may involve buffer handling or memory access operations within the ident service implementation. This limited data exposure represents a classic case of information disclosure where attackers can extract potentially sensitive metadata or file headers, though not full file contents. The underlying issue is consistent with CWE-276, which addresses improper file permissions and inadequate access control mechanisms in Unix-like systems.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to gather intelligence about system configurations and potentially identify sensitive data patterns. Remote attackers can exploit this weakness to discover system administrator credentials, file system structures, or other metadata that could aid in further attacks. The vulnerability's remote nature means that attackers do not require local access or credentials to exploit it, making it particularly dangerous in networked environments. The fact that the attack targets files accessible by the wheel group indicates that attackers could potentially extract information about privileged user accounts, system binaries, or configuration files that might reveal system architecture or security weaknesses. This information gathering capability aligns with ATT&CK technique T1083, which involves discovering system information through reconnaissance activities. The vulnerability's exploitation can lead to privilege escalation opportunities, as attackers might use the gathered information to craft more sophisticated attacks or identify additional system weaknesses.
Mitigation strategies for CVE-2001-0196 require immediate system updates to newer FreeBSD versions where the ident server implementation has been corrected. System administrators should disable the ident service if it is not required for network operations, as this eliminates the attack surface entirely. The recommended approach includes implementing proper access control lists and ensuring that group permissions are correctly enforced throughout the system. Security hardening procedures should include verifying that network services properly manage privileges and do not inadvertently expose sensitive file contents. Organizations should also implement network segmentation and firewall rules to limit access to the ident service ports, typically port 113. The vulnerability highlights the importance of proper privilege separation in network services and demonstrates how seemingly minor permission handling flaws can lead to significant security implications. Regular security audits should verify that all network services properly enforce access controls and that group-based permissions are correctly implemented to prevent similar issues from arising in other system components.