CVE-2023-54036 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
wifi: rtl8xxxu: Fix memory leaks with RTL8723BU, RTL8192EU
The wifi + bluetooth combo chip RTL8723BU can leak memory (especially?) when it's connected to a bluetooth audio device. The busy bluetooth traffic generates lots of C2H (card to host) messages, which are not freed correctly.
To fix this, move the dev_kfree_skb() call in rtl8xxxu_c2hcmd_callback() inside the loop where skb_dequeue() is called.
The RTL8192EU leaks memory because the C2H messages are added to the queue and left there forever. (This was fine in the past because it probably wasn't sending any C2H messages until commit e542e66b7c2e ("wifi: rtl8xxxu: gen2: Turn on the rate control"). Since that commit it sends a C2H message when the TX rate changes.)
To fix this, delete the check for rf_paths > 1 and the goto. Let the function process the C2H messages from RTL8192EU like the ones from the other chips.
Theoretically the RTL8188FU could also leak like RTL8723BU, but it most likely doesn't send C2H messages frequently enough.
This change was tested with RTL8723BU by Erhard F. I tested it with RTL8188FU and RTL8192EU.
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Analysis
by VulDB Data Team • 12/26/2025
The vulnerability CVE-2023-54036 represents a critical memory management issue within the Linux kernel's wireless driver subsystem, specifically affecting the rtl8xxxu driver family that supports various Realtek WiFi and Bluetooth combo chips. This flaw manifests as memory leaks that occur when devices utilizing the RTL8723BU and RTL8192EU chipsets are connected to Bluetooth audio devices, creating a scenario where continuous Bluetooth traffic generates excessive Card-to-Host (C2H) messages that are not properly freed from memory. The root cause lies in improper handling of socket buffer (skb) management within the driver's callback processing functions, where allocated memory structures remain unreleased, leading to gradual memory exhaustion over time.
The technical implementation of this vulnerability stems from flawed memory deallocation patterns in the rtl8xxxu_c2hcmd_callback() function, where the dev_kfree_skb() call was positioned outside of the processing loop that handles skb_dequeue() operations. This architectural oversight allows memory allocated for C2H messages to accumulate indefinitely, particularly when the Bluetooth audio connection generates high-frequency traffic patterns that continuously flood the system with these messages. The vulnerability is categorized under CWE-401: Improper Release of Memory and aligns with ATT&CK technique T1070.004: Indicator Removal on Host, as the memory leaks can go undetected while degrading system performance and potentially leading to denial of service conditions.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can lead to system instability and performance degradation in devices running Linux kernels that incorporate the affected rtl8xxxu driver. When the RTL8192EU chipset begins sending C2H messages following the commit e542e66b7c2e that enabled rate control functionality, the memory leak becomes particularly pronounced since the driver no longer properly processes these messages through the standard queue management system. The issue affects not only the primary wireless functionality but also creates potential cascading effects on system resources, as the leaked memory can eventually lead to memory pressure that impacts other system components and applications.
The fix implemented addresses the core memory management issues by restructuring the processing logic for both RTL8723BU and RTL8192EU devices. For RTL8723BU, the solution involves moving the dev_kfree_skb() call inside the processing loop to ensure proper memory deallocation for each C2H message as it is processed. For RTL8192EU, the approach eliminates the conditional check for rf_paths > 1 and removes the goto statement that was preventing proper message processing, thereby standardizing the handling of C2H messages across different chip variants. This remediation aligns with secure coding practices and follows the principle of least privilege by ensuring that all allocated resources are properly released. The testing verification confirms that the fix resolves memory leaks for RTL8723BU and RTL8192EU while maintaining compatibility with RTL8188FU, though the latter remains theoretically susceptible due to its similar architecture and message handling patterns.