CVE-2026-90009 scsi: bsg: Fix TOCTOU in io_uring passthrough command setup
A time-of-check time-of-use race condition in the Linux kernel's SCSI BSG driver allows local attackers to trigger a buffer overflow and potentially execute code or escalate privileges.
- 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-2026-90009?
CVE-2026-90009 is a high-severity vulnerability in Linux, published on 16 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:
scsi: bsg: Fix TOCTOU in io_uring passthrough command setup
scsi_bsg_uring_cmd() reads bsg_uring_cmd from the shared mmap'd SQE. Userspace can change a field after we check it and before we use it. request_len is the sharp case: it can grow past sizeof(scmd->cmnd) after the bound check and overflow scmd->cmnd in copy_from_user().
READ_ONCE() the SQE fields we check or use into locals before use.
Which versions are affected by CVE-2026-90009?
How do I fix CVE-2026-90009?
Apply the vendor's patch.
Is CVE-2026-90009 being exploited?
There is no known exploitation of CVE-2026-90009 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90009, GHSA-22qm-w4f2-g533, UBUNTU-CVE-2026-90009.