CVE-2026-80951 i3c: master: svc: bound IBI payload to the requested max_payload_len
A missing bounds check in the Linux kernel I3C master driver allows an adjacent device to trigger an out-of-bounds write, potentially leading to code execution or privilege escalation.
- 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-2026-80951?
CVE-2026-80951 is a memory corruption vulnerability in Linux, published on 11 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: master: svc: bound IBI payload to the requested max_payload_len
svc_i3c_master_handle_ibi() reads the IBI payload from the RX FIFO into the IBI slot. The loop is bounded by the hardware FIFO size (SVC_I3C_FIFO_SIZE), not by the slot size.
slot->data points into the IBI pool, which i3c_generic_ibi_alloc_pool() sizes at max_payload_len per slot. svc_i3c_master_request_ibi() only rejects a max_payload_len larger than SVC_I3C_FIFO_SIZE, so a driver can request a smaller one. mctp-i3c requests 1. Each readsb() then copies the controller RXCOUNT bytes (up to 31) with no check against the slot size. A device that sends more bytes than the slot holds writes past slot->data, an out-of-bounds write into the IBI pool.
Bound the loop by dev->ibi->max_payload_len and clamp each read to the space left in the slot, the same way dw-i3c does. A device can still send more than the requested payload. Flush the leftover bytes from the RX FIFO so they do not leak into the next transfer.
Which versions are affected by CVE-2026-80951?
How do I fix CVE-2026-80951?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-80951 being exploited?
There is no known exploitation of CVE-2026-80951 in the wild and no public exploit code.
Sources
Also known as AZL-100136, BELL-CVE-2026-80951, DEBIAN-CVE-2026-80951, GHSA-j6x8-pq79-v84j, UBUNTU-CVE-2026-80951.