CVE-2002-1644 in SSH
Summary
by MITRE
SSH Secure Shell for Servers and SSH Secure Shell for Workstations 2.0.13 through 3.2.1, when running without a PTY, does not call setsid to remove the child process from the process group of the parent process, which allows attackers to gain certain privileges.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2002-1644 affects SSH Secure Shell implementations version 2.0.13 through 3.2.1, specifically when operating without a pseudo-terminal. This flaw represents a critical security weakness that stems from improper process management during SSH session establishment. The vulnerability manifests when the SSH server or workstation component fails to invoke the setsid system call, which is essential for detaching child processes from their parent's process group. This omission creates a privilege escalation vector that can be exploited by malicious actors to gain elevated system access.
The technical root cause of this vulnerability lies in the improper handling of process groups within the SSH implementation. When SSH operates without a PTY, the child process should execute setsid to create a new session and detach itself from the parent's process group. Without this critical step, the child process remains associated with the parent's process group, creating a potential attack surface. This behavior aligns with CWE-254, which addresses weaknesses in process management and session handling. The vulnerability enables attackers to manipulate process relationships and potentially escalate privileges through techniques that exploit the parent-child process dependencies.
From an operational impact perspective, this vulnerability allows attackers to gain certain privileges that should normally be restricted to authorized users. The privilege escalation occurs because the lack of proper process group separation enables attackers to manipulate the SSH session in ways that bypass normal security boundaries. This weakness is particularly dangerous in multi-user environments where SSH is commonly used for remote access and system administration. The vulnerability affects both server and workstation implementations, making it a widespread concern across various deployment scenarios. According to ATT&CK framework, this represents a privilege escalation technique under the T1068 category, specifically targeting process manipulation and session hijacking.
The exploitation of this vulnerability typically involves an attacker establishing an SSH connection without a PTY and then leveraging the process group relationship to gain elevated privileges. The attack requires understanding of process management concepts and the specific implementation details of the affected SSH versions. Security professionals should note that this vulnerability was particularly concerning during the early 2000s when SSH implementations were more commonly deployed in enterprise environments. The lack of proper setsid invocation creates a persistent security gap that can be exploited by attackers with basic system access, potentially leading to complete system compromise. Organizations should implement immediate mitigations including upgrading to patched versions of SSH Secure Shell, implementing proper process isolation mechanisms, and monitoring for suspicious SSH session behaviors that might indicate exploitation attempts.