CVE-2004-0609 in rssh
Summary
by MITRE
rssh 2.0 through 2.1.x expands command line arguments before entering a chroot jail which allows remote authenticated users to determine the existence of files in a directory outside the jail.
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Analysis
by VulDB Data Team • 06/30/2021
The vulnerability identified as CVE-2004-0609 affects rssh versions 2.0 through 2.1.x and represents a critical security flaw in the restricted shell implementation. This issue stems from the improper handling of command line arguments within the rssh framework, specifically during the chroot jail process. The vulnerability allows authenticated remote attackers to perform file system enumeration outside the designated chroot environment, effectively bypassing the security controls intended to contain user access.
The technical flaw manifests when rssh processes command line arguments before executing the chroot system call. During this pre-chroot phase, the application performs argument expansion that occurs in the original file system context rather than within the restricted chroot environment. This timing issue enables attackers to leverage the expanded arguments to probe directory structures and file existence outside the intended jail boundaries. The vulnerability is classified under CWE-22 as Improper Limitation of a Pathname to a Restricted Directory, which specifically addresses path traversal issues in restricted environments.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with reconnaissance capabilities that can be leveraged for more sophisticated attacks. An authenticated user can exploit this flaw to determine which files and directories exist outside the chroot jail, potentially revealing sensitive system information such as configuration files, backup locations, or other system resources that should remain hidden. This reconnaissance capability significantly increases the attack surface and can aid in planning subsequent exploitation attempts.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1083 for File and Directory Discovery. Attackers can utilize this vulnerability to map the target system's file structure without requiring direct access to the restricted shell environment. The vulnerability also relates to privilege escalation techniques since it allows attackers to gather information that could be used to identify system weaknesses or locate sensitive files that might be exploitable through other means.
The recommended mitigation strategy involves upgrading to rssh version 2.2 or later, which addresses this specific issue by ensuring command line argument expansion occurs within the chroot environment. Organizations should also implement additional security controls such as monitoring for unusual argument expansion patterns, conducting regular security audits of restricted shell configurations, and ensuring proper access controls are in place to minimize the impact of potential exploitation. Network segmentation and limiting the number of authenticated users with access to restricted shells can further reduce the risk associated with this vulnerability.