# CVE-2026-31590

> Vulnerability · severity: **MEDIUM** (CVSS 5.5).

## Description

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

KVM: SEV: Drop WARN on large size for KVM_MEMORY_ENCRYPT_REG_REGION

Drop the WARN in sev_pin_memory() on npages overflowing an int, as the
WARN is comically trivially to trigger from userspace, e.g. by doing:

  struct kvm_enc_region range = {
          .addr = 0,
          .size = -1ul,
  };

  __vm_ioctl(vm, KVM_MEMORY_ENCRYPT_REG_REGION, &range);

Note, the checks in sev_mem_enc_register_region() that presumably exist to
verify the incoming address+size are completely worthless, as both "addr"
and "size" are u64s and SEV is 64-bit only, i.e. they _can't_ be greater
than ULONG_MAX.  That wart will be cleaned up in the near future.

	if (range->addr > ULONG_MAX || range->size > ULONG_MAX)
		return -EINVAL;

Opportunistically add a comment to explain why the code calculates the
number of pages the "hard" way, e.g. instead of just shifting @ulen.

## Key facts

- **CVE ID:** CVE-2026-31590
- **Published:** 2026-04-24
- **CVSS severity:** MEDIUM
- **CVSS base score:** 5.5
- **CWE codes:** NVD-CWE-noinfo

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31590

## Citation

> AI Analytics. CVE-2026-31590. Retrieved 2026-08-08 from https://api.ai-analytics.org/cve/CVE-2026-31590. Derived from NIST NVD. Licensed CC0.

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