CVE-2023-54227: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54227 is a memory resource leak vulnerability in the Linux kernel's block multi-queue (blk-mq) subsystem, specifically in the tag management logic when shrinking the number of hardware queues (nr_hw_queues). When the number of hardware queues is reduced, the kernel correctly avoids reallocating set->tags[], but fails to free the tags associated with the removed queues, resulting in a memory leak. The vulnerability was published on December 30, 2025, and affects Linux kernel versions prior to the fixes introduced in stable commits targeting the 6.5.5 and 6.6 patch series. Feedly estimates the severity as Medium, with an EPSS score of 0.00018 (Feedly, EUVD).

The root cause is a missing deallocation path in the blk-mq subsystem (CWE-401: Missing Release of Memory after Effective Lifetime). When nr_hw_queues is shrunk, the code path responsible for resizing the tag set does not free the tags for queues that are being removed — only the tags for the remaining queues are freed upon device teardown. The bug can be reproduced by loading the null_blk driver with multiple submit queues, powering on the device, reducing the queue count, and then removing the device; the tags allocated for the original (larger) queue count are never freed. Fixes were applied via two stable kernel commits: c0ef7493e68b (targeting the 6.5.5 series) and e1dd7bc93029 (targeting the 6.6 series) (Feedly, Kernel Stable c0ef, Kernel Stable e1dd).

The primary impact of CVE-2023-54227 is a kernel memory leak, which can gradually exhaust available memory resources on affected systems over time, particularly in environments where block device queue counts are dynamically adjusted. This can degrade system performance and, in extreme cases, contribute to denial-of-service conditions due to memory exhaustion. There is no known confidentiality or integrity impact, and the vulnerability does not enable remote code execution or privilege escalation (Feedly).

Apply the upstream Linux kernel patches that resolve this issue: commit c0ef7493e68b8896806a2f598fcffbaa97333405 for the 6.5.x stable series and commit e1dd7bc93029024af5688253b0c05181d6e01f8e for the 6.6 stable series. Linux distribution maintainers (e.g., Red Hat, Ubuntu, SUSE) should be monitored for backported fixes in their respective kernel packages. As a workaround, avoid dynamically reducing nr_hw_queues on block devices in production environments until a patched kernel is deployed (Kernel Stable c0ef, Kernel Stable e1dd).