CVE-2025-38469 in Linux
Summary
by MITRE • 07/28/2025
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/xen: Fix cleanup logic in emulation of Xen schedop poll hypercalls
kvm_xen_schedop_poll does a kmalloc_array() when a VM polls the host for more than one event channel potr (nr_ports > 1).
After the kmalloc_array(), the error paths need to go through the "out" label, but the call to kvm_read_guest_virt() does not.
[Adjusted commit message. - Paolo]
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Analysis
by VulDB Data Team • 01/25/2026
The vulnerability CVE-2025-38469 represents a critical memory management flaw within the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem, specifically affecting x86 and Xen hypervisor implementations. This issue manifests in the emulation logic for Xen scheduler operations, particularly the poll hypercalls that facilitate communication between virtual machines and the host system. The flaw occurs when a virtual machine attempts to poll multiple event channel ports simultaneously, creating a scenario where the kernel allocates memory using kmalloc_array() but fails to properly handle cleanup operations in error conditions.
The technical root cause lies in the improper error handling within the kvm_xen_schedop_poll function, which demonstrates a classic memory leak vulnerability pattern. When nr_ports exceeds one, the function allocates memory dynamically to accommodate multiple event channel polling operations, but subsequent error paths do not consistently traverse the designated cleanup label. This creates a situation where allocated memory remains unreleased when error conditions occur, leading to potential resource exhaustion and system instability. The vulnerability specifically affects the interaction between KVM and Xen hypervisors, where the kernel's virtualization layer fails to maintain proper memory lifecycle management during hypercall processing.
The operational impact of this vulnerability extends beyond simple memory leaks, potentially enabling denial of service conditions that could compromise the stability of virtualized environments. Attackers could exploit this weakness by crafting malicious guest VMs that repeatedly invoke the problematic poll hypercall with multiple ports, gradually consuming available memory resources until system performance degrades or crashes occur. The vulnerability affects systems running Linux kernels with KVM virtualization enabled and Xen hypervisor support, making it particularly relevant for cloud computing environments, virtual desktop infrastructures, and server consolidation scenarios where multiple VMs operate concurrently. This flaw represents a significant concern for security-conscious organizations relying on virtualized infrastructure, as it could be leveraged to disrupt critical services or potentially escalate privileges through resource exhaustion attacks.
Mitigation strategies should prioritize immediate kernel updates from vendors to address the memory management error in the KVM subsystem. System administrators should implement monitoring for unusual memory consumption patterns in virtualized environments and consider limiting the number of concurrent event channel polls in guest VMs until patches are applied. The vulnerability aligns with CWE-401 (Improper Release of Memory) and demonstrates characteristics consistent with ATT&CK technique T1499.004 (Resource Hijacking) where attackers exploit memory management flaws to consume system resources. Organizations should also consider implementing virtualization-specific security controls and regular vulnerability assessments to identify similar memory management issues in their virtualized environments, particularly focusing on hypercall processing and memory allocation routines within hypervisor implementations.