CVE-2026-74655
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel's qcom-geni UART driver, there is an issue with flushing the TX DMA buffer during transmission, causing the UART to get stuck infinitely repeating corrupted TX DMA frames. The DMA-mode uart_ops lacks a flush_buffer callback, and the stop path is broken, leading to a hang.
Risk Assessment
The vulnerability can be triggered from userspace with a large write followed by TCOFLUSH, causing a permanent hang of the serial port, potentially affecting embedded systems.
Recommendation
Apply the kernel patch that adds a flush_buffer callback for DMA mode, stops the transfer, clears tx_remaining and tx_queued, and fixes the stop path (cancel command, reset state, wait before unmapping).
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: serial: qcom-geni: fix TX DMA buffer flush When transmit flushing a qcom-geni UART during an ongoing TX DMA, the UART gets stuck infinitely repeating corrupted TX DMA frames. The DMA-mode uart_ops does not provide a flush_buffer callback, so an in-flight transfer can complete after serial core has reset the transmit kfifo, underflowing its length and resubmitting page-sized transfers indefinitely. Add one that stops the transfer and clears tx_remaining and tx_queued. The stop path was also broken: it unmapped the buffer while the serial engine could still read it, and never reset the TX DMA state machine. Cancel the main sequencer command first, then reset the state machine and wait for it before unmapping. Drop the early return so a pending mapping is also cleaned up when the main command is inactive. The bug can be triggered from userspace with a large write immediately followed by TCOFLUSH. A following tcdrain will hang forever. The bug was reproduced and this fix was validated on Arduino Uno Q (QRB2210) using /dev/ttyHS1.

