CVE-2014-6268 in Xen
Summary
by MITRE
The evtchn_fifo_set_pending function in Xen 4.4.x allows local guest users to cause a denial of service (host crash) via vectors involving an uninitialized FIFO-based event channel control block when (1) binding or (2) moving an event to a different VCPU.
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Analysis
by VulDB Data Team • 02/15/2022
The vulnerability described in CVE-2014-6268 represents a critical denial of service flaw within the Xen hypervisor version 4.4.x family. This issue specifically targets the evtchn_fifo_set_pending function which manages event channel operations in virtualized environments. The flaw occurs when local guest users manipulate event channel control blocks through FIFO-based mechanisms, creating conditions that can lead to complete host system crashes. The vulnerability is particularly concerning because it allows unprivileged guest operating systems to potentially bring down the entire host infrastructure, undermining the fundamental security model of virtualization.
The technical root cause of this vulnerability lies in improper initialization of FIFO-based event channel control blocks during critical operations. When guest users perform binding or moving operations on event channels, the evtchn_fifo_set_pending function fails to properly initialize the underlying data structures before processing these operations. This uninitialized state creates exploitable conditions where memory corruption can occur, leading to unpredictable behavior including kernel panics and system crashes. The vulnerability specifically manifests when event channels are either bound to virtual cpu cores or relocated between different vcpu contexts, making it particularly dangerous in multi-tenant virtualized environments where multiple guests share the same physical host.
From an operational impact perspective, this vulnerability enables local privilege escalation attacks that can result in complete system compromise and denial of service for all virtual machines running on the affected host. The attack vector requires only local access within a guest operating system, making it particularly dangerous as it can be exploited by malicious users who have gained access to any virtual machine within the environment. According to CWE-457, this represents a use of uninitialized variable vulnerability that can lead to arbitrary code execution and system instability. The ATT&CK framework categorizes this under privilege escalation techniques, as attackers can leverage this flaw to gain control over the host system and potentially access other virtual machines running on the same infrastructure.
Mitigation strategies for CVE-2014-6268 should focus on immediate patching of affected Xen hypervisor versions, as the vulnerability was addressed in subsequent releases through proper initialization of event channel control blocks. System administrators should implement monitoring for unusual event channel operations and establish strict access controls for virtual machine management interfaces. The fix typically involves ensuring that all FIFO-based event channel control blocks are properly initialized before any binding or movement operations occur, preventing the uninitialized memory access that leads to system crashes. Additionally, organizations should consider implementing hypervisor hardening measures and regular security assessments to identify similar vulnerabilities in virtualization infrastructure components.