CVE-2024-35893 is a vulnerability identified in the Linux kernel's networking subsystem, specifically within the traffic control (tc) module's skbmod action (act_skbmod). The vulnerability arises from an information leak caused by uninitialized memory being copied from kernel space to user space. The root cause is that the 'struct tc_skbmod' contains a four-byte padding hole that is not cleared before the structure's fields are filled. Consequently, when the function tcf_skbmod_dump() copies this structure to user space, it inadvertently leaks kernel stack memory contents. This was detected by syzbot and confirmed by Kernel Memory Sanitizer (KMSAN) warnings indicating kernel-infoleak during copy_to_user operations. The vulnerability involves multiple kernel functions related to network packet handling and netlink messaging, including skb_copy_datagram_iter, netlink_recvmsg, and rtnetlink_rcv_msg, which are part of the Linux kernel's networking stack. The flaw allows an unprivileged user with the ability to interact with the traffic control netlink interface to potentially read sensitive kernel memory. This could expose confidential information residing in kernel memory, such as cryptographic keys, kernel pointers, or other sensitive data. The vulnerability does not appear to require elevated privileges beyond those needed to interact with the traffic control subsystem, nor does it require user interaction beyond sending crafted netlink messages. No known exploits are reported in the wild as of the publication date. The issue has been addressed by clearing the structure before populating it to prevent leakage of uninitialized memory. However, no official patch links are provided in the data. The vulnerability affects Linux kernel versions identified by the commit hash 86da71b57383d40993cb90baafb3735cffe5d800, which likely corresponds to a recent kernel version prior to the fix. Given the Linux kernel's widespread use in servers, desktops, embedded systems, and cloud infrastructure, this vulnerability has broad potential impact.

For European organizations, the impact of CVE-2024-35893 can be significant, especially for those relying heavily on Linux-based infrastructure. The vulnerability enables an information leak from kernel memory, which can undermine confidentiality by exposing sensitive data such as cryptographic keys, credentials, or internal kernel pointers. This exposure can facilitate further attacks, including privilege escalation or kernel exploitation, if attackers combine this leak with other vulnerabilities. Organizations operating critical infrastructure, cloud services, or data centers running Linux kernels with the vulnerable versions are at risk. The leak could compromise data privacy obligations under regulations like GDPR if sensitive personal or corporate data is exposed. Additionally, sectors such as finance, telecommunications, healthcare, and government agencies in Europe that depend on Linux servers and network appliances could face increased risk of targeted attacks leveraging this vulnerability. Although no active exploits are known, the ease of triggering the leak via netlink messages and the lack of need for high privileges or user interaction increase the threat potential. The vulnerability could also affect embedded Linux devices used in industrial control systems or IoT deployments within Europe, potentially impacting operational technology security. Overall, the confidentiality breach risk and the potential for follow-on attacks make this vulnerability a concern for European organizations with Linux deployments.

European organizations should implement the following specific mitigations: 1) Apply the latest Linux kernel updates that include the fix for CVE-2024-35893 as soon as they become available from their Linux distribution vendors or kernel maintainers. 2) Restrict access to the traffic control netlink interface (used for configuring network traffic control) to trusted and authorized users only, using Linux capabilities and access control mechanisms such as SELinux, AppArmor, or seccomp filters. 3) Monitor and audit netlink socket usage and traffic control commands for unusual or unauthorized activity that could indicate exploitation attempts. 4) For environments where immediate patching is not feasible, consider disabling or limiting the use of the skbmod action or traffic control features that invoke the vulnerable code paths, if operationally acceptable. 5) Employ kernel hardening techniques and runtime protections such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce the impact of potential information leaks. 6) Incorporate vulnerability scanning and continuous monitoring tools that can detect the presence of vulnerable kernel versions and alert on attempts to exploit netlink interfaces. 7) Educate system administrators and security teams about this vulnerability to ensure rapid response and patch management. These measures go beyond generic advice by focusing on controlling access to the vulnerable interface and monitoring specific kernel networking components.