CVE-2026-64283
KVM: guest_memfd: Treat memslot binding offset+size as unsigned values
Description
In the Linux kernel, the following vulnerability has been resolved: KVM: guest_memfd: Treat memslot binding offset+size as unsigned values 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).
INFO
Published Date :
July 25, 2026, 10:17 a.m.
Last Modified :
Aug. 17, 2026, 5:17 a.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update the Linux kernel to the latest version.
- Apply patches related to KVM memslot handling.
- Ensure offset and size are treated as unsigned.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-64283.
| URL | Resource |
|---|---|
| https://git.kernel.org/stable/c/eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6 | Patch |
| https://git.kernel.org/stable/c/f3a98d5881b9bd4807f49156143565f6aabcef1e | Patch |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-64283 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-64283
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-64283 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-64283 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Aug. 17, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'f3a98d5881b9bd4807f49156143565f6aabcef1e', 'versionType': 'git'}, {'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6', 'versionType': 'git'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.8'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.8', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '7.1.4', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'affected'}] [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'f3a98d5881b9bd4807f49156143565f6aabcef1e', 'versionType': 'git'}, {'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6', 'versionType': 'git'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.8'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.8', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '7.1.4', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'affected'}] -
Initial Analysis by [email protected]
Aug. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-190 Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.8 up to (excluding) 7.1.4 Added Reference Type kernel.org: https://git.kernel.org/stable/c/eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/f3a98d5881b9bd4807f49156143565f6aabcef1e Types: Patch -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 25, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'f3a98d5881b9bd4807f49156143565f6aabcef1e', 'versionType': 'git'}, {'status': 'affected', 'version': 'a7800aa80ea4d5356b8474c2302812e9d4926fa6', 'lessThan': 'eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6', 'versionType': 'git'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.8'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.8', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '7.1.4', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['virt/kvm/guest_memfd.c', 'virt/kvm/kvm_mm.h'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: KVM: guest_memfd: Treat memslot binding offset+size as unsigned values 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). Added Reference https://git.kernel.org/stable/c/eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6 Added Reference https://git.kernel.org/stable/c/f3a98d5881b9bd4807f49156143565f6aabcef1e