CVE-2023-54036: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54036 is a memory leak vulnerability in the Linux kernel's rtl8xxxu Wi-Fi driver, affecting the RTL8723BU and RTL8192EU USB Wi-Fi chipsets. The flaw causes kernel memory to be leaked when C2H (card-to-host) messages are not properly freed in the rtl8xxxu_c2hcmd_callback() function. It was published on December 24, 2025, and affects Linux kernel versions from commit e542e66b7c2e onward, with fixes backported to stable releases 5.10.173, 5.15.99, 6.1.16, 6.2.3, and 6.3. No CVSS score has been assigned by NVD at this time; Feedly estimates the severity as Medium (Feedly, NVD).

The root cause is improper memory management (CWE category: memory leak) in the rtl8xxxu driver's C2H message handling. For RTL8723BU, the dev_kfree_skb() call in rtl8xxxu_c2hcmd_callback() was placed outside the dequeue loop, meaning only the last dequeued socket buffer was freed while others accumulated. For RTL8192EU, a misplaced rf_paths > 1 check caused C2H messages to be enqueued but never processed or freed — a condition triggered by commit e542e66b7c2e ("wifi: rtl8xxxu: gen2: Turn on the rate control"), which introduced TX rate-change C2H messages. The vulnerability is local in nature, triggered by normal device operation (e.g., active Bluetooth audio traffic on RTL8723BU or TX rate changes on RTL8192EU) rather than by external attacker input (NVD, Feedly).

The primary impact is a gradual kernel memory exhaustion on systems using RTL8723BU or RTL8192EU USB Wi-Fi adapters. Under heavy Bluetooth audio traffic (RTL8723BU) or frequent TX rate changes (RTL8192EU), the kernel heap is progressively depleted, which can degrade system performance and ultimately lead to an out-of-memory condition or system instability. This is a local availability impact with no known confidentiality or integrity consequences, and no lateral movement potential (NVD).

The fix has been backported to multiple stable Linux kernel branches. Patched versions include 5.10.173, 5.15.99, 6.1.16, 6.2.3, and 6.3. The upstream fixes are available in the following kernel.org commits: 35fb0e275af1, 430f9f9bec53, 93c3f34ec02f, b39f662ce164, and f39a86b4efd2. Users should update to a patched kernel version; as a temporary workaround, avoiding use of RTL8723BU with active Bluetooth audio or limiting TX rate changes on RTL8192EU may reduce memory leak frequency, but upgrading the kernel is the recommended solution (NVD, Feedly).