CVE-2026-64267 fuse: avoid 32-bit prune notification count wrap

What is CVE-2026-64267?

CVE-2026-64267 is a medium-severity 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:

fuse: avoid 32-bit prune notification count wrap

FUSE_NOTIFY_PRUNE validates the nodeid payload length with:

size - sizeof(outarg) != outarg.count * sizeof(u64)

On 32-bit kernels, size_t is also 32 bits, so the daemon-controlled count multiplication can wrap. A prune notification with count 0x20000000 and no nodeid payload passes the check, enters the copy loop, and asks the device copy path to read nodeids that are not present in the userspace write buffer. In QEMU this reaches the fuse_copy_fill() BUG_ON(!err) path.

Validate the payload length with array_size() instead. That accepts exactly the same valid messages, but avoids wrapping arithmetic before the copy loop consumes the count.

Which versions are affected by CVE-2026-64267?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-64267?

Apply the vendor's patch.

Is CVE-2026-64267 being exploited?

There is no known exploitation of CVE-2026-64267 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-64267, DEBIAN-CVE-2026-64267, GHSA-pj3g-7699-4m62, ROOT-OS-UBUNTU-2204-CVE-2026-64267, UBUNTU-CVE-2026-64267.