CVE-2026-43061 serial: 8250: Fix TX deadlock when using DMA
A race condition in the Linux kernel's 8250 serial driver causes a TX deadlock when DMA is used, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43061?
CVE-2026-43061 is a medium-severity denial of service vulnerability in Linux kernel, published on 5 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-667
Which versions are affected by CVE-2026-43061?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43061?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43061 being exploited?
There is no known exploitation of CVE-2026-43061 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43061, DEBIAN-CVE-2026-43061, GHSA-6grr-36f8-j7pv, ROOT-OS-DEBIAN-11-CVE-2026-43061, ROOT-OS-UBUNTU-2204-CVE-2026-43061, ROOT-OS-UBUNTU-2404-CVE-2026-43061 and 1 more.