CVE-2026-90386 i3c: dw: avoid shift-out-of-bounds when DAA assigns no devices
A shift-out-of-bounds error in the Linux kernel I3C driver causes a crash when no devices are assigned during boot, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90386?
CVE-2026-90386 is a 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:
i3c: dw: avoid shift-out-of-bounds when DAA assigns no devices
On an empty bus ENTDAA assigns nothing, so cmd->rx_len (the count of addresses left unassigned) equals master->maxdevs.
The GENMASK() index master->maxdevs - cmd->rx_len - 1 then becomes -1, which trips up UBSAN. This happens every time on boot on a Gigabyte/AMD server:
UBSAN: shift-out-of-bounds in drivers/i3c/master/dw-i3c-master.c:905:12 shift exponent 64 is too large for 64-bit type 'long unsigned int' CPU: 7 UID: 0 PID: 963 Comm: (udev-worker) Not tainted 7.0.11-200.fc44.x86_64 #1 PREEMPT(lazy) Hardware name: Giga Computing E163-Z34-AAH1-000/MZ33-DC1-000, BIOS R32_F45 04/01/2026 Call Trace: <TASK> dump_stack_lvl+0x5d/0x80 ubsan_epilogue+0x5/0x2b __ubsan_handle_shift_out_of_bounds.cold+0xd7/0x1ab dw_i3c_master_daa.cold+0x1b/0x96 [dw_i3c_master] i3c_master_do_daa_ext.part.0+0x3e/0xf0 [i3c]
Skip the mask when no new device was assigned.
Which versions are affected by CVE-2026-90386?
How do I fix CVE-2026-90386?
Apply the vendor's patch.
Is CVE-2026-90386 being exploited?
There is no known exploitation of CVE-2026-90386 in the wild and no public exploit code.
Sources
Also known as AZL-102134, BELL-CVE-2026-90386, DEBIAN-CVE-2026-90386, GHSA-hx2c-jppg-3c5r, UBUNTU-CVE-2026-90386.