CVE-2026-64402 coresight: ultrasoc-smb: Fix OOB write in smb_sync_perf_buffer()

High 7.8 Published 25 Jul 2026 Updated 17 Aug 2026

An out-of-bounds write in the Linux kernel's Coresight SMB driver allows attackers to potentially execute code or escalate privileges when using the SMB sink as a perf AUX sink.

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-2026-64402?

CVE-2026-64402 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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:

coresight: ultrasoc-smb: Fix OOB write in smb_sync_perf_buffer()

When the SMB sink is used as a perf AUX sink, smb_update_buffer() calls smb_sync_perf_buffer() to copy hardware trace data into the perf AUX ring buffer pages. It derives pg_idx = head >> PAGE_SHIFT from @head, which is handle->head, and indexes dst_pages[pg_idx]. The pg_idx %= nr_pages normalization is only applied after the first loop iteration.

This leaves the initial page index underived from the buffer size, which can result in an out-of-bounds write past dst_pages[] when head exceeds the AUX buffer size.

Normalize head modulo the AUX buffer size before deriving the page index and offset, mirroring tmc_etr_sync_perf_buffer().

Weakness: CWE-787

Which versions are affected by CVE-2026-64402?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-64402?

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-2026-64402 being exploited?

There is no known exploitation of CVE-2026-64402 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2026-64402, DEBIAN-CVE-2026-64402, GHSA-c5fx-2729-67qq, ROOT-OS-UBUNTU-2204-CVE-2026-64402, UBUNTU-CVE-2026-64402.