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CVE-2026-64300
perf/aux: Fix page UAF in map_range()
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem kernel/events. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64300 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
kernel/events/core.c
- What this is
- PERFORMANCE EVENTS SUBSYSTEMMAINTAINERS section matched on kernel/events/* · linux-perf-users@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_PERF_EVENTS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_PERF_EVENTS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-25 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- kernel/events
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.14 | 6.18.39 | c8b7e113f7b6 |
| 6.14 | 7.1.4 | 0cff05bd2186 |
| 6.14 | 7.2 | 5948aaf64f81 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- Exploitation uses local perf_event_open(), ioctl(), mmap(), and munmap() operations; no network or physical path reaches map_range().
- AC:LAttack complexity, low
- The attacker controls both racing mappings and the freeing munmap(), can enlarge the AUX allocation window, and can retry without depending on victim-controlled conditions.
- PR:LPrivileges required, low
- An ordinary unprivileged user can create task-scoped AUX events such as Intel PT with exclude_kernel enabled under the upstream default perf_event_paranoid setting.
- UI:NUser interaction, none
- The attacking process independently creates the events, races the mappings, frees the AUX buffer, and accesses the stale mapping without victim action.
- S:UScope, unchanged
- Exploitation compromises the host kernel from local userspace but does not inherently cross a separate virtualization or IOMMU security authority.
- C:HConfidentiality impact, high
- The persistent VM_PFNMAP alias exposes whichever kernel allocation reuses the freed physical frame, enabling disclosure of sensitive kernel memory.
- I:HIntegrity impact, high
- The stale page is mapped at offset zero, where pfn_mkwrite permits writes, enabling corruption of a reused kernel page and potential control-flow hijacking.
- A:HAvailability impact, high
- Writing through the stale PFN can corrupt arbitrary kernel-owned page contents and cause an oops, panic, or complete system compromise.