CVE-2026-53124 ublk: reset per-IO canceled flag on each fetch
A flaw in the Linux kernel ublk driver can cause a denial of service if the ublk server crashes during device recovery, leaving IOs stuck.
- 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-2026-53124?
CVE-2026-53124 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Jun 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:
ublk: reset per-IO canceled flag on each fetch
If a ublk server starts recovering devices but dies before issuing fetch commands for all IOs, cancellation of the fetch commands that were successfully issued may never complete. This is because the per-IO canceled flag can remain set even after the fetch for that IO has been submitted - the per-IO canceled flags for all IOs in a queue are reset together only once all IOs for that queue have been fetched. So if a nonempty proper subset of the IOs for a queue are fetched when the ublk server dies, the IOs in that subset will never successfully be canceled, as their canceled flags remain set, and this prevents ublk_cancel_cmd from actually calling io_uring_cmd_done on the commands, despite the fact that they are outstanding.
Fix this by resetting the per-IO cancel flags immediately when each IO is fetched instead of waiting for all IOs for the queue (which may never happen).
Which versions are affected by CVE-2026-53124?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53124?
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-2026-53124 being exploited?
There is no known exploitation of CVE-2026-53124 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53124, DEBIAN-CVE-2026-53124, GHSA-xq85-jg4p-xf7w, UBUNTU-CVE-2026-53124.