CVE-2026-43061: serial: 8250: Fix TX deadlock when using DMA

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-05 · updated 2026-06-17
Weakness: CWE-667

Description

In the Linux kernel, the following vulnerability has been resolved: serial: 8250: Fix TX deadlock when using DMA `dmaengine_terminate_async` does not guarantee that the `__dma_tx_complete` callback will run. The callback is currently the only place where `dma->tx_running` gets cleared. If the transaction is canceled and the callback never runs, then `dma->tx_running` will never get cleared and we will never schedule new TX DMA transactions again. This change makes it so we clear `dma->tx_running` after we terminate the DMA transaction. This is "safe" because `serial8250_tx_dma_flush` is holding the UART port lock. The first thing the callback does is also grab the UART port lock, so access to `dma->tx_running` is serialized.

Affected products

Linux kernel: from 5.4.291 before 5.5; from 5.10.235 before 5.10.253; from 5.15.179 before 5.15.203; from 6.1.129 before 6.1.167; from 6.6.79 before 6.6.130; from 6.12.16 before 6.12.78 — fixed in 5.10.253, 5.15.203, 5.5, 6.1.167, 6.12.78, 6.14

How to fix

Upgrade to a fixed version: Linux kernel 5.10.253, 5.15.203, 5.5, 6.1.167. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-43061 or the next vulnerability affects your stack