CVE-2025-39803: 
Linux Debian vulnerability analysis and mitigation

CVE-2025-39803 is a vulnerability discovered in the Linux kernel, specifically in the SCSI UFS core component. The issue was disclosed on September 15, 2025, affecting the UIC completion interrupt handling in the ufshcd_uic_cmd_compl() function. The vulnerability primarily impacts Linux kernel systems that utilize the UFS (Universal Flash Storage) subsystem (NVD, Debian Tracker).

The vulnerability occurs when the UIC completion interrupt is disabled while a UIC command is being processed. Upon re-enabling the UIC completion interrupt, an UIC interrupt is triggered, causing a WARN_ON_ONCE(!cmd) statement to be hit. This issue was addressed by removing the kernel warning from the ufshcd_uic_cmd_compl() function (NVD, Debian Tracker).

The impact of this vulnerability appears to be limited to system logging and debugging functionality, as it primarily involves a kernel warning mechanism. The issue affects systems running vulnerable versions of the Linux kernel with UFS storage implementations (Debian Tracker).

The vulnerability has been resolved through a kernel patch that removes the problematic WARN_ON_ONCE() call from the ufshcd_uic_cmd_compl() function. Various Linux distributions have incorporated the fix, including Debian's bullseye, bookworm, and trixie releases (Debian Tracker).