CVE-2024-35944 is a vulnerability identified in the Linux kernel's VMCI (Virtual Machine Communication Interface) subsystem, specifically within the function dg_dispatch_as_host located in the vmci_datagram.c driver code. The issue arises from an unsafe use of memcpy() where a field-spanning write occurs. The memcpy operation copies data from a source datagram structure to a destination structure that includes a fixed-size message field and a flexible array member for the payload. The vulnerability is triggered when the payload_size is manipulated (e.g., by fuzzing with Syzkaller) to a value larger than expected, causing memcpy to write beyond the bounds of the fixed-size msg field and into adjacent memory areas. This behavior results in a runtime warning under FORTIFY_SOURCE protections and indicates a potential buffer overflow condition. The root cause is that memcpy is copying the entire datagram size (header plus payload) into a structure where the msg field is only 24 bytes, but the payload can be larger, leading to an overlap and memory corruption. The suggested fix involves splitting the memcpy into two operations: one copying the fixed-size msg structure and another copying the variable-length payload separately, thus preventing the field-spanning write and ensuring memory safety. Although no known exploits are currently reported in the wild, this vulnerability could be leveraged to cause memory corruption, potentially leading to denial of service or privilege escalation in environments using VMCI, such as virtualized Linux hosts running VMware products. The vulnerability affects multiple versions of the Linux kernel identified by specific commit hashes, indicating it is present in recent kernel builds prior to the fix.

For European organizations, the impact of CVE-2024-35944 depends largely on their use of Linux systems with VMCI enabled, which is common in virtualized environments, especially those leveraging VMware virtualization technology on Linux hosts. Successful exploitation could allow attackers to corrupt kernel memory, potentially leading to system crashes (denial of service) or privilege escalation, compromising the confidentiality, integrity, and availability of critical systems. This is particularly concerning for sectors with high reliance on virtualized infrastructure such as finance, telecommunications, government, and cloud service providers across Europe. The vulnerability could disrupt business operations, lead to data breaches, or enable lateral movement within networks. Given the kernel-level nature of the flaw, the impact could be severe if exploited, affecting the stability and security of virtualized workloads. However, the lack of known exploits and the requirement for local code execution or privileged access to trigger the vulnerability somewhat limits the immediate risk. Nonetheless, the widespread use of Linux in European data centers and enterprises means that unpatched systems remain vulnerable to potential future exploit development.

European organizations should prioritize applying the official Linux kernel patches that address this vulnerability by correcting the memcpy usage in the VMCI datagram handling code. Specifically, kernel maintainers have recommended splitting the memcpy operation into two distinct copies to avoid field-spanning writes. Organizations running VMware virtualization on Linux hosts should ensure their kernel versions are updated to include this fix. Additionally, system administrators should audit their environments to identify Linux hosts with VMCI enabled and restrict access to these systems to trusted users only, minimizing the risk of local exploitation. Employing kernel hardening techniques such as enabling FORTIFY_SOURCE, stack canaries, and kernel address space layout randomization (KASLR) can provide additional layers of defense. Monitoring system logs for unusual kernel warnings or crashes related to vmci_datagram.c may help detect attempted exploitation. Finally, organizations should maintain robust vulnerability management processes to track Linux kernel updates and apply security patches promptly.