high 7.0

CVE-2026-64283 json

KVM: guest_memfd: Treat memslot binding offset+size as unsigned values

published 2026-07-25 3 mo ago modified 2026-11-06 2 d ago also EUVD-2026-48995

cvss: 7.0; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 4%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

When binding a memslot to a guest_memfd file, treat the offset and size as unsigned values to fix a bug where the sum of the two can result in a false negative when checking for overflow against the size of the file. Passing unsigned values also avoids relying on somewhat obscure checks in other flows for safety, and tracks the offset and size as they are intended to be tracked, as unsigned values.

On 64-bit kernels, the number of pages a memslot contains and thus the size (and offset) of its guest_memfd binding are unsigned 64-bit values. Taking the offset+size as an loff_t instead of a uoff_t inadvertently converts the unsigned value to a signed value if the offset and/or size is massive.

Locally storing the offset and size as signed values is benign in and of itself (though even that is *extremely* difficult to discern), but operating on their sum is not.

For the offset, KVM explicitly checks against a negative value, which might seem like a bug as KVM could incorrectly reject a legitimate binding, but that's not actually the case as KVM_CREATE_GUEST_MEMFD takes a signed value for its size, i.e. a would-be-negative offset is also greater than the maximum possible size of any guest_memfd file.

Regarding the size, while KVM lacks an explicit check for a negative value, i.e. seemingly has a flawed overflow check, KVM restricts the number of pages in a single memslot to the largest positive signed 32-bit value:

if (id < KVM_USER_MEM_SLOTS && (mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES) return -EINVAL;

and so that maximum "size" will ever be is 0x7fffffff000.

The sum of the two is, however, problematic. While the size is restricted by KVM's memslot logic, the offset is not, i.e. the offset is completely unchecked until the "offset + size > i_size_read(inode)" check. If the offset is the (nearly) largest possible _positive_ value, then adding size to the offset can result in a signed, negative 64-bit value. When compared against the size of the file (guaranteed to be positive), the negative sum is always smaller, and KVM incorrectly allows the absurd offset.

Opportunistically add missing includes in kvm_mm.h (instead of relying on its parents).

Patch / fix

fixed in 1 distros 4 links 4

Linux Linux 6.12.114, 6.18.57, 7.1.4, 7.2

debian ubuntu suse opensuse

linux Debian 13 6.12.115-2
linux Debian 14 7.1.4-1

debian advisories DEBIAN-CVE-2026-64283

linux Ubuntu 26.04 LTS 7.0.0-31.31
linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
linux-gcp Ubuntu 26.04 LTS 7.0.0-1011.11
linux-gke Ubuntu 26.04 LTS 7.0.0-1006.7
linux-ibm Ubuntu 26.04 LTS 7.0.0-1013.13
linux-azure Ubuntu 26.04 LTS 7.0.0-1014.14
linux-raspi Ubuntu 26.04 LTS 7.0.0-1019.19
linux-riscv Ubuntu 26.04 LTS 7.0.0-31.31.1

ubuntu advisories UBUNTU-CVE-2026-64283

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.84.1
kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.84.1
kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1.150700.17.47.1

suse advisories SUSE-SU-2026:4706-1 SUSE-SU-2026:4640-1 SUSE-SU-2026:24316-1 SUSE-SU-2026:24315-1 SUSE-SU-2026:24181-1 SUSE-SU-2026:24182-1

kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1 openSUSE-SU-2026:11476-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64283 updated 2026-11-05 cvss 7.0

kernel: KVM: guest_memfd: Treat memslot binding offset+size as unsigned values

Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 d ago (2026-11-06)

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.0	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Linux Linux

Classification

Weakness

CWE-190 Integer Overflow or Wraparound

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-64283
NVD CVE-2026-64283

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary