CVE-2004-2073 in Linux-Vserver
Summary
by MITRE
Linux-VServer 1.24 allows local users with root privileges on a virtual server to gain access to the filesystem outside the virtual server via a modified chroot-again exploit using the chmod command.
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2004-2073 represents a critical privilege escalation flaw within Linux-VServer version 1.24 that undermines the fundamental security isolation mechanisms designed to protect virtual server environments. This vulnerability specifically targets the chroot functionality that is essential for maintaining containerized security boundaries between virtual servers. The exploit leverages a modified chroot-again technique that exploits weaknesses in how the system handles file permissions and access controls when transitioning between virtual server contexts. The flaw occurs when local users with root privileges within a virtual server can manipulate the chmod command to bypass the intended filesystem boundaries and access resources outside their designated virtual environment.
The technical implementation of this vulnerability stems from inadequate permission checking and path validation mechanisms within the Linux-VServer implementation. When a root user executes the modified chroot-again exploit, the system fails to properly validate the target filesystem paths, allowing malicious operations to traverse beyond the intended virtual server boundaries. The chmod command serves as the vehicle for this exploitation by manipulating file permissions in ways that can expose or grant access to files and directories outside the virtual server's designated filesystem scope. This represents a direct violation of the principle of least privilege and demonstrates a failure in the security model that should prevent cross-contamination between virtual server environments.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally compromises the security architecture of virtualized environments. An attacker who successfully exploits this vulnerability can access sensitive data, modify system files, and potentially escalate their privileges to gain full control over the host system. The implications are particularly severe in multi-tenant hosting environments where multiple virtual servers share the same physical host, as this vulnerability can enable one compromised virtual server to access resources belonging to other virtual servers. The attack vector is particularly concerning because it requires only local root access within a single virtual server, making it relatively easy to exploit compared to remote attacks that require additional reconnaissance and exploitation steps.
This vulnerability maps directly to CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-264, which covers permissions, privileges, and access controls. The attack pattern aligns with techniques described in the ATT&CK framework under T1068, which covers "Exploitation for Privilege Escalation," and T1565, which covers "Data Manipulation" through privilege escalation attacks. Organizations implementing Linux-VServer or similar virtualization solutions should consider this vulnerability as a critical security concern that directly impacts their ability to maintain secure multi-tenant environments. The remediation process requires immediate patching of the Linux-VServer implementation to properly validate filesystem paths and implement stricter access controls when executing chmod operations within virtual server contexts. System administrators must also implement additional monitoring and logging to detect potential exploitation attempts and ensure that virtual server boundaries remain intact across all hosting environments.