CVE-2017-10913 in Xen
Summary
by MITRE
The grant-table feature in Xen through 4.8.x provides false mapping information in certain cases of concurrent unmap calls, which allows backend attackers to obtain sensitive information or gain privileges, aka XSA-218 bug 1.
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Analysis
by VulDB Data Team • 12/30/2020
The CVE-2017-10913 vulnerability represents a critical flaw in the Xen hypervisor's grant table implementation that affects versions through 4.8.x. This vulnerability operates at the hypervisor level and fundamentally undermines the memory isolation guarantees that virtual machines depend upon for security. The grant table mechanism serves as a crucial component for sharing memory pages between different virtual machines and the host system, making it a prime target for attackers seeking to escalate privileges or extract sensitive information. The flaw specifically manifests during concurrent unmap operations where the hypervisor fails to properly maintain consistent mapping information, creating a race condition that can be exploited by malicious actors.
The technical root cause of this vulnerability lies in the improper handling of memory mapping updates within the grant table subsystem. When multiple unmap operations occur simultaneously, the hypervisor's internal data structures fail to maintain atomic consistency, leading to stale or incorrect mapping entries being returned to requesting domains. This behavior creates a scenario where an attacker can manipulate the mapping information to access memory regions that should be restricted, potentially allowing them to read sensitive data from other virtual machines or even the host system itself. The vulnerability operates under CWE-362 which specifically addresses race conditions, and it aligns with ATT&CK technique T1055.011 for privilege escalation through hypervisor manipulation.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential privilege escalation capabilities that could allow attackers to compromise entire virtualized environments. Attackers can exploit this weakness to gain unauthorized access to memory contents of other virtual machines, potentially extracting confidential data, credentials, or system information that should remain isolated. In cloud computing environments where multiple tenants share the same physical infrastructure, this vulnerability could enable a malicious tenant to access resources belonging to other tenants, fundamentally breaking the security model that virtualization platforms are designed to maintain. The exploitability of this vulnerability is particularly concerning because it requires minimal privileges to execute and can be leveraged to undermine the core security guarantees of virtualization technology.
Mitigation strategies for CVE-2017-10913 primarily focus on upgrading to patched versions of the Xen hypervisor where the grant table race condition has been resolved. Organizations should immediately implement patches released by Xen Project and their respective vendors to address the underlying race condition in the grant table implementation. Additionally, monitoring systems should be enhanced to detect anomalous memory mapping behavior that might indicate exploitation attempts. Network segmentation and access controls should be strengthened to limit the potential impact of successful exploitation, while also implementing proper hypervisor hardening practices. Regular security assessments of virtualized environments are essential to identify and remediate similar vulnerabilities that may exist in other components of the virtualization stack, ensuring comprehensive protection against hypervisor-based attacks that target the fundamental isolation mechanisms of virtualized computing environments.