CVE-2008-0216 in FreeBSD
Summary
by MITRE
The ptsname function in FreeBSD 6.0 through 7.0-PRERELEASE does not properly verify that a certain portion of a device name is associated with a pty of a user who is calling the pt_chown function, which might allow local users to read data from the pty from another user.
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Analysis
by VulDB Data Team • 09/15/2018
The vulnerability identified as CVE-2008-0216 represents a critical privilege escalation and information disclosure flaw within the FreeBSD operating system's pseudo-terminal (pty) subsystem. This issue affects FreeBSD versions 6.0 through 7.0-PRERELEASE and stems from improper validation within the ptsname function implementation. The flaw specifically targets the verification process that occurs when a user attempts to change ownership of a pseudo-terminal device through the pt_chown function call. The vulnerability manifests when the system fails to properly authenticate that a device name portion corresponds to a pty belonging to the calling user, creating a potential pathway for unauthorized access to another user's pseudo-terminal communications.
The technical exploitation of this vulnerability relies on the improper validation of device name associations within the pty subsystem. When the ptsname function processes a device name, it should verify that the calling user has legitimate ownership or access rights to the specific pty device being referenced. However, due to insufficient validation checks, an attacker can manipulate the device name parameter to reference a pty belonging to another user. This misconfiguration allows local users to bypass normal access controls and potentially read sensitive data transmitted through the targeted pseudo-terminal. The vulnerability operates at the kernel level within the device name resolution process, making it particularly dangerous as it can be exploited without requiring elevated privileges beyond normal user access.
The operational impact of CVE-2008-0216 extends beyond simple information disclosure to encompass potential privilege escalation and data integrity concerns. Local attackers can exploit this vulnerability to access communications between other users and their terminal sessions, potentially intercepting sensitive information such as passwords, confidential commands, or proprietary data transmitted through pseudo-terminals. The flaw particularly affects environments where multiple users share a single FreeBSD system and rely on pseudo-terminal functionality for remote access or shell sessions. This vulnerability undermines the fundamental security model of pseudo-terminal access control and could enable attackers to compromise user sessions, leading to unauthorized system access or data exfiltration. The impact is especially severe in multi-user environments where users may be conducting sensitive operations through terminal sessions.
Mitigation strategies for this vulnerability require immediate system updates and patches from FreeBSD security advisories, as the flaw exists within core operating system components. System administrators should implement the latest FreeBSD security patches that address the improper validation within the ptsname function and strengthen the verification process for pty device access. Additionally, monitoring for unauthorized access attempts to pseudo-terminal devices should be enhanced through system logging and audit configurations. The vulnerability aligns with CWE-264, which addresses permissions, privileges, and access controls, and can be mapped to ATT&CK technique T1068, which covers privilege escalation through local exploits. Organizations should also consider implementing additional access controls and monitoring mechanisms to detect potential exploitation attempts, as the vulnerability may be used in conjunction with other local privilege escalation techniques to gain further system access.