CVE-2026-64300 perf/aux: Fix page UAF in map_range()
A race condition in the Linux kernel perf subsystem allows a use-after-free of memory pages, potentially enabling local attackers to execute arbitrary 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-2026-64300?
CVE-2026-64300 is a high-severity use after free 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:
perf/aux: Fix page UAF in map_range()
map_range() reads rb->aux_pages[], rb->aux_nr_pages and rb->aux_pgoff via perf_mmap_to_page() while holding only event->mmap_mutex. Those fields are serialized by rb->aux_mutex, and mmap_mutex is per event.
Thus, two events sharing one rb via PERF_EVENT_IOC_SET_OUTPUT can race rb_alloc_aux() with map_range(), leading to a page-UAF scenario as follows:
CPU 0 CPU 1 ===== ===== rb_alloc_aux() map_range() [1]: allocate rb->aux_pages[0] [2]: rb->aux_nr_pages++ [3]: perf_mmap_to_page() returns rb->aux_pages[0] [4]: map it as VM_PFNMAP [5]: rb->aux_pgoff = 1
munmap the page [6]: free rb->aux_pages[0]
Pages mapped as VM_PFNMAP have no refcount protection, so CPU 1 holds a mapping to a freed physical frame.
Fix this by taking rb->aux_mutex across the page walk in map_range().
Weakness: CWE-416
Which versions are affected by CVE-2026-64300?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64300?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-64300 being exploited?
There is no known exploitation of CVE-2026-64300 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64300, DEBIAN-CVE-2026-64300, GHSA-643v-c574-jxr9, ROOT-OS-UBUNTU-2204-CVE-2026-64300, UBUNTU-CVE-2026-64300.