CVE-2008-4405 in xen
Summary
by MITRE
xend in Xen 3.0.3 does not properly limit the contents of the /local/domain xenstore directory tree, and does not properly restrict a guest VM s write access within this tree, which allows guest OS users to cause a denial of service and possibly have unspecified other impact by writing to (1) console/tty, (2) console/limit, or (3) image/device-model-pid. NOTE: this issue was originally reported as an issue in libvirt 0.3.3 and xenstore, but CVE is considering the core issue to be related to Xen.
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Analysis
by VulDB Data Team • 12/27/2024
The vulnerability described in CVE-2008-4405 represents a critical security flaw in the Xen hypervisor version 3.0.3 that affects the xend management daemon and the xenstore directory tree implementation. This issue stems from insufficient access controls and content validation within the xenstore namespace, which serves as the primary communication channel between the hypervisor and guest virtual machines. The vulnerability specifically targets the /local/domain directory tree structure where guest operating systems can interact with hypervisor-managed resources through xenstore operations. The flaw allows malicious guest OS users to manipulate critical system components by writing to specific xenstore paths that should be restricted to hypervisor-level processes only. This represents a fundamental breakdown in the hypervisor's privilege separation mechanisms and demonstrates a classic case of insufficient input validation and access control enforcement.
The technical exploitation of this vulnerability occurs through three primary attack vectors within the xenstore namespace: console/tty, console/limit, and image/device-model-pid paths. When guest VMs write to these locations without proper restrictions, they can trigger system instability and denial of service conditions that effectively compromise the availability of the virtualized environment. The console/tty path allows manipulation of console output handling, while console/limit controls the console output buffer size, and image/device-model-pid references to the device model process identifier. These write operations can cause xend to crash or enter an inconsistent state, leading to complete system unavailability. The vulnerability is particularly dangerous because it operates at the hypervisor level where guest OS users can leverage these unrestricted write operations to affect the entire virtualization infrastructure rather than just their individual VM. This aligns with CWE-264, which addresses privileges, permissions, and access controls, and represents a privilege escalation scenario where guest users gain unauthorized system-level capabilities.
The operational impact of CVE-2008-4405 extends beyond simple denial of service to potentially enable more sophisticated attacks that could compromise the integrity and availability of the entire virtualized platform. An attacker could repeatedly exploit these vulnerabilities to cause persistent system outages, making the virtualized environment unreliable for production workloads. The unspecified other impacts mentioned in the CVE description suggest that this vulnerability might provide opportunities for information disclosure, privilege escalation, or even remote code execution depending on the specific implementation details and system configuration. Organizations using Xen 3.0.3 are particularly vulnerable because this version predates many security hardening measures that were subsequently implemented in later releases. The vulnerability affects the fundamental architecture of the hypervisor's resource management system and demonstrates a critical failure in the principle of least privilege enforcement. This flaw can be categorized under ATT&CK technique T1059, which involves executing malicious code through command and scripting interpreters, and more specifically relates to T1499 for network denial of service attacks. The vulnerability also connects to ATT&CK technique T1068, which involves exploiting vulnerabilities in the operating system or hypervisor itself.
Mitigation strategies for this vulnerability require immediate patching of the Xen hypervisor to a version that properly implements access controls and content validation for the xenstore directory tree. Organizations should implement strict xenstore access controls and monitor for unauthorized write operations to critical paths within the /local/domain namespace. Network segmentation and hypervisor-level monitoring should be deployed to detect and prevent exploitation attempts. The recommended solution involves updating to Xen 3.1 or later versions where proper access control mechanisms have been implemented to restrict guest VMs from writing to sensitive xenstore paths. Additionally, implementing hypervisor-level logging and alerting for xenstore operations can help detect potential exploitation attempts. System administrators should also consider disabling unnecessary xenstore access for guest VMs and implementing proper privilege separation between hypervisor components and guest operating systems. The vulnerability highlights the importance of proper input validation and access control enforcement in virtualization platforms, and serves as a reminder that hypervisor-level security flaws can have catastrophic consequences for entire virtualized infrastructures. Organizations should also implement regular security assessments of their virtualization environments to identify similar privilege escalation opportunities that could lead to system compromise.