CVE-2017-8904 in Xen
Summary
by MITRE
Xen through 4.8.x mishandles the "contains segment descriptors" property during GNTTABOP_transfer (aka guest transfer) operations, which might allow PV guest OS users to execute arbitrary code on the host OS, aka XSA-214.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-8904 represents a critical security flaw in the Xen hypervisor affecting versions 4.8.x and earlier. This issue specifically manifests during GNTTABOP_transfer operations, which are part of the grant table interface used for memory sharing between guest operating systems and the host hypervisor. The vulnerability stems from improper handling of the "contains segment descriptors" property within these guest transfer operations, creating a potential pathway for privilege escalation attacks.
The technical flaw occurs when Xen processes guest transfer requests that involve grant tables containing segment descriptors. The hypervisor fails to properly validate or sanitize the segment descriptor information during these operations, allowing malicious guest operating systems to manipulate the grant table entries in ways that bypass normal access controls. This misconfiguration enables a guest operating system to craft specially crafted grant table entries that, when processed by the host hypervisor, can lead to unauthorized code execution within the host environment. The vulnerability specifically affects paravirtualized (PV) guest operating systems that utilize the grant table mechanism for memory sharing and inter-vm communication.
From an operational impact perspective, this vulnerability represents a severe threat to virtualized environments as it allows a compromised guest OS to escalate privileges and execute arbitrary code on the host system. Attackers can leverage this flaw to break out of the guest isolation boundaries and gain control over the underlying hypervisor, potentially affecting all virtual machines running on the same host. This creates a cascading security risk where a single compromised guest can compromise the entire virtualization infrastructure. The vulnerability is particularly dangerous in multi-tenant cloud environments where multiple customers share the same physical hardware and hypervisor infrastructure.
Mitigation strategies for CVE-2017-8904 require immediate patching of affected Xen hypervisor versions to 4.8.1 or later, which contain the necessary fixes for proper validation of segment descriptors during guest transfer operations. Organizations should also implement network segmentation and access controls to limit guest OS capabilities, while monitoring for suspicious grant table activity. The vulnerability aligns with CWE-119 Improper Access Control and CWE-200 Information Disclosure, and maps to ATT&CK technique T1055 Process Injection and T1068 Exploitation for Privilege Escalation. System administrators should conduct comprehensive vulnerability assessments of their virtualization infrastructure and ensure all guest operating systems are updated to prevent exploitation of this critical flaw that undermines the fundamental security model of virtualized environments.