CVE-2026-64283KVM: 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).

Timeline

Scores

EPSS (exploitation in 30 days)

0.15% · top 96% of all CVEs (14 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.0.

Affected products

• Linux · Linux

  • affected a7800aa80ea4d5356b8474c2302812e9d4926fa6 – < e4683654881f3303ab286e45df6f91c0675d867c
  • affected a7800aa80ea4d5356b8474c2302812e9d4926fa6 – < 3f9c0fdefa0431ad7a5528d76b9cdad912500bdf
  • affected a7800aa80ea4d5356b8474c2302812e9d4926fa6 – < f3a98d5881b9bd4807f49156143565f6aabcef1e
  • affected a7800aa80ea4d5356b8474c2302812e9d4926fa6 – < eba85fee7fc6cf28fec38a5bf3c378bef9a79ca6

• Linux · Linux

  • affected 6.8
  • unaffected < 6.8
  • unaffected 6.12.114 – ≤ 6.12.*
  • unaffected 6.18.57 – ≤ 6.18.*
  • unaffected 7.1.4 – ≤ 7.1.*
  • unaffected 7.2 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-48995 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-64283](https://cveledger.app/badge/CVE-2026-64283.svg)](https://cveledger.app/cve/CVE-2026-64283)

Record last updated 6 Nov 2026, 16:34 UTC.