A flaw in the Linux 8250 serial driver prevents the flag that indicates an ongoing DMA transmission from being cleared if the DMA operation is canceled and its completion callback does not execute. Because the flag remains set, subsequent attempts to initiate UART DMA for transmit are blocked, causing the serial port to hang. This defect does not provide privilege escalation or remote code execution; it merely disrupts serial output, which can impact boot sequences, kernel logging, or remote management that relies on UART communication.

The vulnerability affects the Linux kernel’s 8250 serial driver. Kernels built without the patch that clears dma->tx_running after DMA termination are potentially vulnerable. The fix is present in the mainline kernel repository in the referenced commits, so any kernel prior to the inclusion of those commits may be at risk.

The CVSS score of 5.5 indicates a moderate severity, while the EPSS score of < 1% suggests a low likelihood of exploitation, and the vulnerability is not listed in CISA’s KEV catalog. Based on the description, it is inferred that attack requires local or privileged access to trigger a DMA cancellation on an UART device, limiting the attack surface to systems where an attacker can control the serial driver or the hardware configuration. No remote exploitation vector is described. The impact is service disruption rather than data compromise or privilege escalation.