CVE-2026-62432 in Xen
Summary
by MITRE • 07/28/2026
The EVTCHNOP_expand_array hypercall checks for whether FIFO event channels are enabled, but without holding the correct lock. It can race with EVTCHNOP_reset, resulting in dereferencing a NULL pointer.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerability described involves a critical race condition within the EVTCHNOP_expand_array hypercall implementation in virtualization environments. This flaw occurs when the system attempts to expand event channel arrays while simultaneously processing reset operations, creating a scenario where memory access validation fails due to insufficient locking mechanisms. The root cause stems from improper synchronization between concurrent operations that manage event channel state transitions, specifically failing to acquire the necessary exclusive locks before checking FIFO event channel status.
The technical implementation of this vulnerability manifests when the hypercall routine evaluates whether FIFO event channels are enabled without maintaining proper exclusivity through appropriate mutex or spinlock acquisition. This atomicity failure allows for a temporal window where another thread executing EVTCHNOP_reset can modify the underlying data structures while the expansion operation is in progress. The consequence of this race condition is the potential dereferencing of a NULL pointer, which can lead to system crashes, unauthorized access, or privilege escalation depending on the execution context and memory layout.
From an operational standpoint, this vulnerability represents a significant threat to virtual machine integrity and system stability, particularly in environments where multiple concurrent operations manage event channel resources. The race condition creates an unpredictable execution path that may manifest as intermittent system failures or more severe security implications when exploited by malicious actors. Attackers could potentially leverage this flaw to cause denial of service conditions or gain elevated privileges within the hypervisor environment, directly violating the fundamental isolation guarantees that virtualization platforms are designed to maintain.
The vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming scenarios where improper synchronization leads to unpredictable behavior. Additionally, this issue maps to ATT&CK technique T1059.001 related to command and scripting interpreter execution, as exploitation could enable attackers to execute arbitrary code within the hypervisor context. The flaw also intersects with defense evasion tactics through potential privilege escalation mechanisms that could bypass normal access controls.
Mitigation strategies should focus on implementing proper locking mechanisms around the event channel expansion logic, ensuring that all shared data structures are protected by appropriate synchronization primitives before any state validation occurs. System administrators should prioritize patching affected virtualization platforms and implementing monitoring solutions to detect anomalous hypercall behavior patterns. Additionally, architectural improvements including better resource management policies and enhanced atomic operation handling within the hypervisor kernel can prevent similar race conditions from manifesting in future implementations.