CVE-2026-74655

A flaw was found in the Linux kernel. Specifically, a vulnerability exists in the qcom-geni Universal Asynchronous Receiver-Transmitter (UART) driver's transmit Direct Memory Access (DMA) buffer flush mechanism. A local user can exploit this by initiating a large write operation immediately followed by a TCOFLUSH command. This can cause the UART to become unresponsive, leading to an indefinite hang during subsequent tcdrain calls and resulting in a Denial of Service (DoS).

qcom-geni UART TX DMA flushing can leave an in flight DMA transfer active while the serial core resets the transmit kfifo. A local user can trigger the failure with a large write followed by TCOFLUSH, after which corrupted TX DMA frames may be repeated indefinitely and a later tcdrain can hang. For the CVSS the PR:L is used because a local process must have access to the affected UART device and issue normal tty operations, but full root privileges are not necessarily required if device permissions or a service account allow this access. The issue is not network reachable and requires local access to a Qualcomm GENI UART using DMA mode. Impact is mainly denial of service through a stuck UART TX path and hung waiters. Worst case may include limited confidentiality or integrity impact if DMA reads stale or unintended TX buffer contents and transmits them over the serial line.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.