CVE-2024-35973 is a medium-severity vulnerability in the Linux kernel's geneve network tunneling module. The issue arises from improper header validation in the geneve_xmit_skb function, which handles packet transmission for the Generic Network Virtualization Encapsulation (GENEVE) protocol. The root cause is a discrepancy in how the kernel validates the protocol field in socket buffers (skb). While most IP tunnel helpers use skb_protocol(skb, true) to correctly interpret the protocol, the function pskb_inet_may_pull() only checks skb->protocol directly. This leads to a scenario where if the skb->protocol is neither ETH_P_IPV6 nor ETH_P_IP, pskb_inet_may_pull() does not perform any action, potentially causing the network header pointer to be incorrect and the skb linear part to be smaller than expected. This can result in uninitialized memory usage during packet transmission, as detected by the Kernel Memory Sanitizer (KMSAN) in the geneve_xmit() function. The vulnerability was identified through syzbot fuzz testing and involves complex interactions with VLAN tags and AF_PACKET sockets. The fix involves adding skb_vlan_inet_prepare() to perform comprehensive MAC validation and adjusting protocol handling to ensure correct skb header alignment. The vulnerability affects multiple Linux kernel versions, including recent mainline releases, and requires local privileges with low complexity for exploitation. No user interaction is needed, but privileges are required to send packets through the affected geneve interface. The impact is limited to availability, as the flaw can cause kernel crashes or denial of service due to uninitialized memory usage during packet transmission. Confidentiality and integrity are not directly impacted. No known exploits are currently reported in the wild.

For European organizations, the impact of CVE-2024-35973 primarily concerns systems running Linux kernels with the geneve module enabled, especially in environments utilizing network virtualization, cloud infrastructure, or software-defined networking (SDN) solutions that leverage GENEVE tunnels. Disruption of network services due to kernel crashes or denial of service can affect critical infrastructure, cloud service providers, and enterprises relying on Linux-based virtualized network functions. The vulnerability requires local privileges, so attackers would need access to compromised hosts or insider capabilities to exploit it. However, given the widespread use of Linux in European data centers, telecom networks, and cloud platforms, the potential for service disruption exists, particularly in sectors with high reliance on virtualized networking such as finance, telecommunications, and government. The absence of confidentiality or integrity impact reduces the risk of data breaches, but availability impacts could lead to operational downtime and associated financial and reputational damage.

To mitigate CVE-2024-35973, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from trusted sources or distributions. 2) Audit and monitor systems that utilize GENEVE tunnels, especially those handling VLAN-tagged traffic or AF_PACKET sockets, to detect unusual kernel behavior or crashes. 3) Restrict local user privileges to minimize the risk of exploitation by unprivileged users; ensure that only trusted users have access to systems with geneve interfaces. 4) Employ kernel hardening techniques such as enabling Kernel Address Sanitizer (KASAN) or Kernel Memory Sanitizer (KMSAN) in testing environments to detect similar issues proactively. 5) Consider disabling the geneve module or related network tunneling features if not required, reducing the attack surface. 6) Implement robust network segmentation and access controls to limit exposure of vulnerable hosts. 7) Maintain up-to-date intrusion detection and prevention systems capable of identifying anomalous packet transmission attempts that could trigger the vulnerability.