CVE-1999-1041 in OpenServer
Summary
by MITRE
Buffer overflow in mscreen on SCO OpenServer 5.0 and SCO UNIX 3.2v4 allows a local user to gain root access via (1) a long TERM environmental variable and (2) a long entry in the .mscreenrc file.
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Analysis
by VulDB Data Team • 12/24/2024
The vulnerability identified as CVE-1999-1041 represents a critical buffer overflow flaw in the mscreen application component of SCO OpenServer 5.0 and SCO UNIX 3.2v4 operating systems. This security weakness resides in the handling of environment variables and configuration file entries, creating a pathway for local privilege escalation attacks that can result in complete system compromise. The vulnerability specifically affects the mscreen utility which is used for terminal screen management and display handling within these unix-based systems.
The technical implementation of this buffer overflow occurs through two distinct attack vectors that leverage different input sources. The first vector involves manipulating the TERM environmental variable, which is commonly used to specify the terminal type and capabilities for applications. When a maliciously crafted long TERM variable is set, it overflows the allocated buffer space within mscreen's memory management, potentially allowing attackers to overwrite adjacent memory locations. The second vector targets the .mscreenrc configuration file, where an overly long entry can trigger the same buffer overflow condition during program initialization or configuration parsing. Both attack methods exploit the fundamental flaw in input validation and memory boundary checking within the mscreen application's code structure.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as successful exploitation can provide attackers with root-level access to the affected systems. This elevated privilege level enables comprehensive system control including access to all user accounts, modification of system files, installation of malicious software, and potential use as a foothold for further network infiltration. The local nature of the attack means that an attacker must already have access to the target system, but once achieved, the privilege escalation provides complete administrative control over the affected machine. This vulnerability particularly affects enterprise environments running legacy SCO systems where the mscreen utility is actively used for terminal management.
The underlying technical flaw aligns with CWE-121, which categorizes heap-based buffer overflow conditions, and demonstrates poor input validation practices in memory management. From an attack framework perspective, this vulnerability maps to the privilege escalation techniques documented in the MITRE ATT&CK framework under the privilege escalation tactics, specifically focusing on local exploitation methods. The vulnerability's remediation requires either patching the mscreen application to implement proper buffer size validation and bounds checking, or implementing system-level restrictions such as limiting the length of environment variables and configuration file entries. System administrators should also consider disabling unnecessary terminal management utilities and implementing proper access controls to limit potential exploitation vectors. The vulnerability highlights the importance of robust input validation and memory management practices in legacy system security, particularly in environments where older unix variants continue to operate without proper security updates.