CVE-2017-15591 in Xen
Summary
by MITRE
An issue was discovered in Xen 4.5.x through 4.9.x allowing attackers (who control a stub domain kernel or tool stack) to cause a denial of service (host OS crash) because of a missing comparison (of range start to range end) within the DMOP map/unmap implementation.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/25/2019
The vulnerability identified as CVE-2017-15591 represents a critical denial of service flaw within the Xen hypervisor ecosystem affecting versions 4.5.x through 4.9.x. This issue resides in the Device Model Operations (DMOP) map/unmap implementation which governs how virtual devices interact with guest operating systems through the hypervisor layer. The vulnerability stems from a fundamental logical error in the range validation mechanism that controls memory mapping operations between virtual machines and the host system. Attackers who have gained control over a stub domain kernel or tool stack can exploit this weakness to trigger a host OS crash, effectively compromising system stability and availability.
The technical root cause of this vulnerability manifests as a missing comparison operation between range start and range end parameters within the DMOP implementation. This omission creates a scenario where the hypervisor fails to validate whether a memory range is properly formed, allowing malformed or invalid range specifications to proceed through the mapping process without proper bounds checking. When such invalid ranges are processed, the hypervisor's memory management subsystem encounters undefined behavior that ultimately results in a system crash. The flaw operates at the intersection of hypervisor memory management and device model operations, where the absence of proper range validation creates an execution path that leads to kernel panic conditions. This vulnerability directly maps to CWE-129 Input Validation and CWE-691 Insufficient Control Flow Management, both of which are fundamental security weaknesses in software design that allow for improper handling of boundary conditions.
The operational impact of CVE-2017-15591 extends beyond simple denial of service as it represents a potential pathway for more sophisticated attacks within virtualized environments. Since attackers need only control a stub domain kernel or tool stack to exploit this vulnerability, the attack surface is relatively narrow but highly impactful within compromised virtualized infrastructures. The vulnerability can be leveraged in environments where multiple virtual machines share the same hypervisor host, potentially enabling an attacker to destabilize the entire virtualization platform. This type of vulnerability is particularly concerning in cloud computing environments where many tenants share the same physical hardware, as a single compromised guest could potentially affect the availability of services across multiple customers. The attack vector aligns with ATT&CK technique T1059 Command and Scripting Interpreter, where attackers utilize legitimate system tools to manipulate hypervisor operations, and T1499 Endpoint Denial of Service, which targets system resources to prevent normal operation.
Mitigation strategies for this vulnerability require immediate patching of affected Xen hypervisor versions to the latest stable releases that contain the proper range validation logic. System administrators should prioritize updating all hypervisor components, particularly those running versions 4.5.x through 4.9.x, as the vulnerability has been addressed in subsequent releases through proper implementation of range start to range end comparisons. Additional defensive measures include implementing strict access controls for stub domain kernels and tool stacks, monitoring for anomalous memory mapping operations, and establishing robust intrusion detection systems that can identify potential exploitation attempts. Organizations should also consider implementing network segmentation and virtual machine isolation techniques to limit the potential impact of any successful exploitation attempts. The vulnerability highlights the importance of proper input validation in hypervisor components and serves as a reminder of the critical security considerations required in virtualization environments where multiple security domains interact through shared kernel interfaces.