CVE-2025-38403 in Linux
Summary
by MITRE • 07/25/2025
In the Linux kernel, the following vulnerability has been resolved:
vsock/vmci: Clear the vmci transport packet properly when initializing it
In vmci_transport_packet_init memset the vmci_transport_packet before populating the fields to avoid any uninitialised data being left in the structure.
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability identified as CVE-2025-38403 resides within the Linux kernel's virtual socket (vsock) implementation, specifically affecting the vmci transport packet handling mechanism. This issue represents a classic case of improper memory initialization that could potentially expose sensitive data or create unexpected behavior within the kernel's virtualized communication framework. The vulnerability impacts systems utilizing VMware's virtual machine communication interface transport layer, which facilitates communication between virtual machines and host systems through the vsock subsystem.
The technical flaw manifests in the vmci_transport_packet_init function where memory initialization occurs improperly. Rather than clearing the entire vmci_transport_packet structure before populating its fields, the implementation uses memset to clear the structure only after field population has begun. This sequence leaves uninitialized data remnants within the packet structure that could contain sensitive information from previous operations or contain unpredictable values that might affect system behavior. The vulnerability stems from a fundamental violation of secure coding practices where memory is not properly sanitized before reuse, creating potential attack vectors through information disclosure or privilege escalation opportunities.
The operational impact of this vulnerability extends beyond simple data corruption, as it could enable attackers to extract sensitive information from kernel memory spaces through carefully crafted packet operations. When the vmci transport packet structure is initialized, any uninitialized fields that retain their previous values could contain confidential data such as cryptographic keys, session information, or other sensitive kernel state. This type of vulnerability aligns with CWE-457: Use of Uninitialized Variable and represents a significant concern in kernel security contexts where memory integrity directly impacts system confidentiality and integrity. The issue could potentially be exploited in scenarios where attackers can control packet creation or observe packet contents, creating opportunities for information leakage or further exploitation.
Mitigation strategies for CVE-2025-38403 primarily involve applying the official kernel patch that corrects the memory initialization sequence in the vmci_transport_packet_init function. The fix ensures that the entire packet structure is cleared using memset before any field population occurs, eliminating the possibility of uninitialized data remaining in the structure. System administrators should prioritize updating their kernel versions to include this patch, particularly in environments where vmci transport is actively used or where virtual machine communication is critical. Additionally, monitoring for unusual packet behavior or memory access patterns in systems utilizing vsock with vmci transport could help detect potential exploitation attempts. This vulnerability demonstrates the importance of proper memory management in kernel space and aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, where improper memory handling can create opportunities for attackers to gain elevated privileges or access sensitive information through information disclosure vulnerabilities. Organizations should also implement regular security assessments of their kernel configurations and ensure comprehensive testing of kernel updates before deployment to maintain system integrity and prevent exploitation of similar memory initialization flaws.