CVE-2024-42265 is a vulnerability identified in the Linux kernel related to speculative execution and bounds checking in the function do_dup2(). The issue arises because the kernel code fetches a file descriptor from an array (fdt->fd[fd]) without adequately protecting against speculative execution side effects. Although the code verifies that the file descriptor index (fd) is not greater than the maximum allowed (max_fds), speculative execution by modern CPUs can cause the processor to execute instructions out of order, potentially accessing out-of-bounds array elements speculatively. This speculative access can lead to information leakage or other side-channel attacks similar to those seen in Spectre-class vulnerabilities. The vulnerability is mitigated by using array_index_nospec(), a kernel function designed to prevent speculative execution from accessing out-of-bounds array indices by sanitizing the index during speculative paths. This fix aligns with previous mitigations applied to similar functions like close_fd() and file_close_fd_locked(). The vulnerability does not currently have known exploits in the wild and lacks an assigned CVSS score. However, it represents a subtle but important speculative execution side-channel risk in the Linux kernel's file descriptor management subsystem.

For European organizations, this vulnerability poses a risk primarily in environments running vulnerable Linux kernel versions, especially in servers, cloud infrastructure, and embedded systems. Exploitation could allow an attacker with local access or the ability to run code on the system to leak sensitive kernel memory contents or file descriptor information, potentially exposing confidential data or enabling privilege escalation chains. This could impact confidentiality and integrity of systems handling sensitive personal data, intellectual property, or critical infrastructure operations. Given the widespread use of Linux in European data centers, government agencies, and enterprises, the vulnerability could affect a broad range of sectors including finance, healthcare, telecommunications, and public administration. Although exploitation requires local code execution and is not known to be remotely exploitable, the speculative execution nature means that side-channel attacks could be subtle and difficult to detect, increasing the risk of stealthy data leaks.

European organizations should prioritize updating their Linux kernel to versions that include the patch for CVE-2024-42265. Specifically, they should ensure that the kernel incorporates the use of array_index_nospec() in the do_dup2() function and related file descriptor handling code. System administrators should audit their environments for vulnerable kernel versions and apply vendor-provided security updates promptly. For environments where immediate patching is challenging, organizations should restrict local access to trusted users only, implement strict process isolation, and monitor for unusual local activity that could indicate exploitation attempts. Additionally, enabling kernel-level mitigations for speculative execution vulnerabilities (such as retpoline or other CPU microcode updates) can reduce the risk. Organizations should also review and harden their security posture around local privilege escalation vectors and side-channel attack detection capabilities.