CVE-2026-90323 ublk: validate auto buf reg before taking uring_cmd
A local attacker can cause a kernel hang during teardown by triggering a validation error in ublk auto buffer registration.
- 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-2026-90323?
CVE-2026-90323 is a denial of service vulnerability in Linux, published on 17 Sep 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: validate auto buf reg before taking uring_cmd
With UBLK_F_AUTO_BUF_REG, invalid sqe->addr can fail after ublk_fill_io_cmd() has set UBLK_IO_FLAG_ACTIVE. The uring_cmd is completed while the tag stays active, which can hang teardown.
Split validation from buffer apply so the check has no side effects, then take the uring_cmd and store the already-validated buffer. Apply the same order in FETCH so io->buf is not written before __ublk_fetch() state checks.
Which versions are affected by CVE-2026-90323?
How do I fix CVE-2026-90323?
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-2026-90323 being exploited?
There is no known exploitation of CVE-2026-90323 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-90323, DEBIAN-CVE-2026-90323, GHSA-rq26-mw8f-3hjh, UBUNTU-CVE-2026-90323.