CVE-2014-1666 in Xen
Summary
by MITRE
The do_physdev_op function in Xen 4.1.5, 4.1.6.1, 4.2.2 through 4.2.3, and 4.3.x does not properly restrict access to the (1) PHYSDEVOP_prepare_msix and (2) PHYSDEVOP_release_msix operations, which allows local PV guests to cause a denial of service (host or guest malfunction) or possibly gain privileges via unspecified vectors.
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Analysis
by VulDB Data Team • 06/08/2021
The vulnerability identified as CVE-2014-1666 represents a critical access control flaw within the Xen hypervisor's physical device operation handling mechanism. This issue affects multiple versions of the Xen virtualization platform including 4.1.5, 4.1.6.1, 4.2.2 through 4.2.3, and 4.3.x releases, making it a widespread concern across the virtualization ecosystem. The flaw resides in the do_physdev_op function which governs how physical device operations are processed within the hypervisor environment. This function fails to properly validate and restrict access to two specific operations: PHYSDEVOP_prepare_msix and PHYSDEVOP_release_msix, which are essential for managing message signaled interrupts in virtualized environments. The vulnerability classification aligns with CWE-284, which addresses improper access control, and represents a significant deviation from proper privilege separation between host and guest operating systems.
The technical exploitation of this vulnerability occurs through local paravirtualized (PV) guests that can manipulate the affected physical device operations to either disrupt system functionality or potentially escalate privileges. When a malicious guest attempts to execute these unrestricted operations, the hypervisor's insufficient validation allows the guest to bypass normal access controls that should prevent unauthorized manipulation of physical device resources. This flaw essentially creates a pathway for guest operating systems to directly influence host-level physical device management, which violates fundamental virtualization security principles. The unspecified vectors of attack suggest that the vulnerability could manifest in multiple ways, potentially including memory corruption, interrupt handling disruption, or privilege escalation scenarios that could compromise the entire virtualization environment.
The operational impact of CVE-2014-1666 extends beyond simple denial of service conditions to potentially enable privilege escalation attacks that could compromise the integrity of the entire virtualization platform. Local PV guests can leverage this vulnerability to cause host or guest malfunction, which may result in complete system crashes, data corruption, or unauthorized access to sensitive system resources. The potential for privilege escalation places this vulnerability in a particularly dangerous category as it could allow attackers to gain elevated privileges within the hypervisor environment, potentially leading to complete compromise of all virtual machines running on the affected host. This threat model aligns with ATT&CK technique T1055, which covers privilege escalation through exploitation of software vulnerabilities, and demonstrates how hypervisor-level flaws can cascade into broader security breaches.
Mitigation strategies for this vulnerability require immediate patching of affected Xen versions to address the improper access control in the do_physdev_op function. System administrators should prioritize upgrading to patched versions of Xen where the PHYSDEVOP_prepare_msix and PHYSDEVOP_release_msix operations are properly restricted. Additionally, implementing network segmentation and access controls can help limit the potential impact of exploitation by reducing the attack surface available to local PV guests. Monitoring for suspicious activity related to physical device operations and interrupt handling within virtualized environments can help detect potential exploitation attempts. The vulnerability highlights the importance of proper input validation and access control mechanisms in hypervisor code, as well as the need for comprehensive security testing of virtualization platforms. Organizations should also consider implementing hypervisor hardening measures and regularly reviewing access controls to prevent similar issues from emerging in other components of their virtualization infrastructure.