CVE-2023-53847: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53847 is a vulnerability in the Linux kernel's USB storage alauda subdriver (drivers/usb/storage/alauda.c) caused by use of uninitialized memory in the alauda_check_media() function. The flaw was identified by Syzbot using KMSAN (Kernel Memory Sanitizer) and was published on December 9, 2025. It affects the Linux kernel across multiple stable branches. Feedly estimates the severity as HIGH, with an EPSS score of 0.000240 (Feedly).

The root cause is an uninitialized value access (CWE-457) in alauda_check_media(), which reads data from a USB transfer buffer without first verifying that the transfer completed successfully. If the USB control transfer fails, the buffer contents remain uninitialized, and the function proceeds to use that data — a classic uninit-value bug surfaced by KMSAN. A secondary issue exists in alauda_get_media_status(), where a usb_stor_dbg() call redundantly references potentially uninitialized data on error paths. Additionally, alauda_check_media() performs DMA directly to a stack-allocated buffer, which is an unsafe practice in kernel USB drivers. The fix adds a transfer success check before using the received data, treating a failed transfer as "no media present" (Feedly).

Exploitation of this vulnerability could allow a local attacker or a malicious USB device to trigger kernel reads of uninitialized stack memory, potentially leaking sensitive kernel data (confidentiality impact) or causing unpredictable kernel behavior. In the worst case, the uninitialized data could influence control flow decisions within the USB storage subsystem, potentially leading to a kernel panic or system instability (availability impact). The attack surface is limited to systems with the alauda USB storage subdriver loaded and a USB device attached that can cause transfer failures.

Apply the upstream Linux kernel patches that fix the uninitialized value access in alauda_check_media() and the related issues in alauda_get_media_status(). Patches have been committed to multiple stable kernel branches (referenced by commits 0d2d5282, 7a11d1e2, 044f4446, 49d380bc, and 153c3e85 in the stable kernel tree). Downstream distributions including Amazon Linux 2 (ALAS2KERNEL-5.4-2025-116) and SUSE have issued advisories incorporating these fixes (Amazon Linux Advisory, Linux Security SUSE). As a workaround, systems that do not require the alauda USB storage subdriver can blacklist the alauda kernel module to eliminate the attack surface.