CVE-2023-53811: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53811 is a kernel warning/bug vulnerability in the Linux kernel's RDMA/irdma driver, caused by the driver attempting to use more MSI-X vectors than the number of online CPUs plus one. When the number of configured MSI-X vectors exceeds num_online_cpus() + 1, the kernel triggers a warning in irdma_cfg_ceq_vector because the driver tries to update the IRQ affinity hint with a CPU mask larger than the maximum CPU IDs. The vulnerability affects the Linux kernel's irdma (Intel RDMA) driver. It was published on December 9, 2025, and is estimated as Medium severity with an EPSS score of 0.000180 (Feedly, CVEFeed).

The root cause is an improper bounds check (related to CWE-125/CWE-20 — improper input validation or out-of-bounds read on CPU mask) in the irdma_cfg_ceq_vector function within the Linux kernel's RDMA irdma driver. When the driver is probed via irdma_probe() → irdma_rt_init_hw(), it configures Completion Event Queue (CEQ) vectors and attempts to set IRQ affinity hints using a CPU mask derived from the configured MSI-X count. If the MSI-X vector count exceeds num_online_cpus() + 1, the CPU mask index exceeds the valid range defined in include/linux/cpumask.h:106, triggering a kernel WARN_ON. The fix caps the number of MSI-X vectors used to num_online_cpus() + 1 at driver initialization (Feedly).

The primary impact is a kernel warning (WARN_ON) triggered during driver probe, which can cause instability or unexpected behavior in systems using the Intel RDMA (irdma) driver with a high MSI-X vector configuration. While this does not directly result in arbitrary code execution or privilege escalation, it can degrade system reliability and potentially cause denial-of-service conditions on RDMA-capable systems. The affected asset scope is limited to Linux systems with Intel RDMA hardware using the irdma kernel driver (Feedly).

There is no known public exploit code, active in-the-wild exploitation, or threat actor attribution associated with CVE-2023-53811. The EPSS score is very low at 0.000180, indicating a minimal probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. It is detectable via Nessus (plugin 278107) and Qualys (plugin 761056) (Feedly, Tenable).

The fix has been committed to the Linux kernel stable tree, capping the number of MSI-X vectors used by the irdma driver to num_online_cpus() + 1. Administrators should apply the relevant kernel patches from the stable commits (e.g., 9cd9842c, 209e4aa9, 87674a35, b3bd44bf on kernel.org). Updating to a patched kernel version that includes these fixes is the recommended remediation. As a workaround, limiting the number of MSI-X vectors configured for the irdma device to not exceed num_online_cpus() + 1 may prevent the warning from triggering (Feedly, kernel.org).