CVE-2025-23155 is a vulnerability identified in the Linux kernel's networking subsystem, specifically within the stmmac driver, which is responsible for managing Ethernet MAC hardware. The flaw arises from improper handling of the irq affinity_hint, where a local cpumask variable's pointer is saved into irq_desc and subsequently accessed from procfs. Since the cpumask is a local variable, it becomes a use-after-free scenario when accessed later, potentially leading to undefined behavior such as kernel crashes or memory corruption. The root cause is that the cpumask pointer should not be local because irq_desc retains a reference to it beyond the local scope. The fix involves replacing the local cpumask with a persistent mask obtained via cpumask_of(cpu#), ensuring the pointer remains valid for the lifetime of irq_desc. This vulnerability affects Linux kernel versions prior to the patch and could be triggered by interactions with the network driver, possibly through crafted network traffic or local operations that manipulate IRQ affinity settings. Although no known exploits are reported in the wild, the vulnerability could be leveraged to cause denial of service or potentially escalate privileges by corrupting kernel memory structures.

For European organizations, the impact of CVE-2025-23155 could be significant, especially for those relying on Linux-based infrastructure in critical environments such as telecommunications, cloud services, and industrial control systems. The stmmac driver is commonly used in embedded systems and network devices, which are prevalent in European telecom and manufacturing sectors. Exploitation could lead to system instability, service outages, or kernel panics, affecting availability and operational continuity. While direct remote exploitation may be limited, attackers with local access or the ability to send crafted network packets could trigger the vulnerability. This could facilitate denial of service attacks or serve as a stepping stone for privilege escalation, undermining confidentiality and integrity. Organizations with large-scale Linux deployments, including data centers and IoT devices, may face increased risk if patches are not promptly applied. Additionally, the vulnerability could be exploited in targeted attacks against critical infrastructure, potentially disrupting essential services.

To mitigate CVE-2025-23155, European organizations should prioritize the following actions: 1) Apply the official Linux kernel patches that address the cpumask pointer handling in the stmmac driver as soon as they are available. 2) Conduct an inventory of all systems running affected Linux kernel versions, focusing on network devices and embedded systems using the stmmac driver. 3) Implement strict network segmentation and access controls to limit exposure of vulnerable systems to untrusted networks and users. 4) Monitor kernel logs and system behavior for signs of irregular IRQ affinity changes or kernel crashes that could indicate exploitation attempts. 5) For environments where patching is delayed, consider temporary mitigations such as disabling or restricting the use of the affected network interfaces or drivers if feasible. 6) Incorporate this vulnerability into incident response and vulnerability management workflows to ensure timely detection and remediation. 7) Engage with hardware and software vendors to confirm the availability of patched firmware or kernel versions for embedded devices.