CVE-2008-2573 in FreeSSHD
Summary
by MITRE
Stack-based buffer overflow in SFTP in freeSSHd 1.2.1 allows remote authenticated users to execute arbitrary code via a long directory name in an SSH_FXP_OPENDIR (aka opendir) command.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2008-2573 represents a critical stack-based buffer overflow flaw within the Secure File Transfer Protocol implementation of freeSSHd version 1.2.1. This issue specifically manifests in the handling of directory operations during SFTP sessions, creating a pathway for remote authenticated attackers to escalate privileges and execute arbitrary code on the affected system. The vulnerability resides in the processing of SSH_FXP_OPENDIR commands which are used to open directories for file listing operations within SFTP sessions.
The technical exploitation of this vulnerability occurs through a carefully crafted directory name that exceeds the allocated buffer space within the SFTP server implementation. When an authenticated user sends an SSH_FXP_OPENDIR request containing an excessively long directory path, the software fails to properly validate the input length before copying it to a fixed-size stack buffer. This classic buffer overflow condition allows an attacker to overwrite adjacent memory locations including return addresses and control data, potentially enabling code execution with the privileges of the SFTP service account.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on freeSSHd for secure file transfers, as it requires only authenticated access to exploit. The attack vector is particularly concerning because it operates over the standard SSH protocol, making it difficult to distinguish from legitimate traffic. The impact extends beyond simple code execution to potential privilege escalation and system compromise, especially when the SFTP service runs with elevated privileges. This vulnerability aligns with CWE-121 stack-based buffer overflow, which is classified under the broader category of memory safety issues in software development.
The security implications of this vulnerability are compounded by the fact that it affects a widely used SSH implementation that many organizations deploy for secure file transfers and remote administration. Attackers can leverage this flaw to gain unauthorized access to sensitive data, establish persistent backdoors, or use the compromised system as a pivot point for further attacks within the network infrastructure. The vulnerability also demonstrates the importance of input validation and proper buffer management in network services, as highlighted by ATT&CK technique T1059 for command and scripting interpreter usage and T1068 for exploit for privilege escalation.
Mitigation strategies for CVE-2008-2573 should prioritize immediate patching of the freeSSHd software to version 1.2.2 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should also implement network segmentation to limit access to SFTP services, enforce strict authentication controls, and monitor for unusual directory operations within SFTP sessions. Additional protective measures include configuring firewalls to restrict SSH access to trusted networks, implementing intrusion detection systems to monitor for exploitation attempts, and conducting regular security assessments of SSH implementations. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security software and proper input validation practices in network services.