CVE-2025-21885 is a vulnerability identified in the Linux kernel, specifically affecting the RDMA (Remote Direct Memory Access) subsystem's bnxt_re driver, which is used for Broadcom NetXtreme network adapters. The issue arises when using the NVMe target with the use_srq (Shared Receive Queue) option enabled. The vulnerability is due to improper handling of page size and page shift information for kernel space SRQs, which was previously only set for user space SRQs. This misconfiguration leads to kernel panics caused by divide errors during the creation of SRQs by kernel consumers. The kernel panic logs indicate a failure in the bnxt_qplib_create_srq function, which is responsible for allocating and initializing hardware queues. The root cause is that page size and shift details are not correctly set for kernel space SRQs, leading to erroneous calculations and ultimately a system crash. This vulnerability can cause denial of service (DoS) conditions by crashing the kernel, impacting system availability. Since the flaw is in the kernel driver handling RDMA and NVMe target configurations, it affects systems using these features, particularly those leveraging high-performance storage and networking setups. The vulnerability does not require user interaction but does require the use of specific kernel features (NVMe target with use_srq enabled). No known exploits are reported in the wild as of the publication date. The fix involves setting the page size and page shift correctly for kernel space SRQs, aligning with the handling for user space SRQs.

For European organizations, the impact of CVE-2025-21885 can be significant, especially for enterprises and data centers relying on Linux servers with RDMA-enabled Broadcom network adapters and NVMe storage targets. The vulnerability can cause unexpected kernel panics leading to system crashes and downtime, which affects availability of critical services. Industries such as finance, telecommunications, cloud service providers, and research institutions that use high-performance computing and storage infrastructure are particularly at risk. The denial of service caused by kernel panics can disrupt business operations, lead to data unavailability, and increase operational costs due to system recovery and troubleshooting. Although no direct data breach or privilege escalation is indicated, the loss of availability can indirectly impact confidentiality and integrity if systems are taken offline during attacks or failures. The lack of known exploits reduces immediate risk, but the complexity of the environment and the critical nature of affected systems mean that timely patching is essential to prevent potential exploitation or accidental crashes.

1. Apply the official Linux kernel patches that address CVE-2025-21885 as soon as they become available from trusted sources or Linux distribution vendors. 2. Temporarily disable the use_srq option in NVMe target configurations if patching cannot be immediately performed, to avoid triggering the vulnerability. 3. Monitor kernel logs for signs of divide errors or kernel panics related to bnxt_re or RDMA subsystems to detect potential exploitation or accidental triggering. 4. Conduct thorough testing of RDMA and NVMe target configurations in staging environments before deployment to production to identify any instability. 5. Maintain up-to-date backups and implement robust incident response procedures to quickly recover from potential denial of service events. 6. Engage with hardware vendors to ensure firmware and driver compatibility with patched kernel versions. 7. Limit access to systems using RDMA and NVMe targets to trusted administrators to reduce risk of accidental or malicious triggering of the vulnerability.