CVE-2017-12135 in Xen
Summary
by MITRE
Xen allows local OS guest users to cause a denial of service (crash) or possibly obtain sensitive information or gain privileges via vectors involving transitive grants.
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Analysis
by VulDB Data Team • 11/07/2019
The vulnerability identified as CVE-2017-12135 affects the Xen virtual machine monitor and represents a significant security flaw in the hypervisor's handling of memory management operations. This issue specifically impacts guest operating systems running within Xen virtual machines and enables local users to exploit weaknesses in the transitive grant mechanism that governs memory sharing between virtual machines and the host system. The vulnerability stems from inadequate validation of grant references during memory operations, creating opportunities for malicious code execution or system instability.
The technical flaw manifests through improper handling of transitive grants which are mechanisms used to allow guest operating systems to share memory pages with the hypervisor. When guest users manipulate these grant references in specific ways, they can trigger memory corruption conditions that lead to system crashes or unauthorized access to sensitive data. The vulnerability exists because the hypervisor fails to properly validate the legitimacy of grant references before processing memory operations, allowing attackers to craft malicious grant structures that bypass normal security checks. This weakness particularly affects the grant table management subsystem where memory mappings are established between guest and host environments.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable privilege escalation and information disclosure attacks. Local users within a guest operating system can exploit this flaw to either crash the entire virtual machine or gain elevated privileges within the guest environment, which could then be leveraged to compromise the host system or other virtual machines running on the same hypervisor. The potential for information disclosure means that attackers could access sensitive data that should remain isolated between virtual environments, undermining the fundamental security model of virtualization. This vulnerability particularly concerns cloud service providers and organizations relying on Xen-based virtualization platforms where multiple tenants share the same physical infrastructure.
Mitigation strategies for CVE-2017-12135 primarily focus on applying official security patches provided by Xen Project and maintaining up-to-date virtualization environments. Organizations should prioritize immediate patch deployment across all affected Xen installations and implement monitoring for suspicious memory access patterns that could indicate exploitation attempts. The vulnerability aligns with CWE-125, which addresses out-of-bounds read conditions, and CWE-264, which covers permissions, privileges, and access controls. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1055 for privilege escalation and T1499 for denial of service, making it a critical target for both defensive and offensive security operations. System administrators should also consider implementing additional isolation measures and monitoring for anomalous grant table operations to detect potential exploitation attempts.