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

> A double-free vulnerability in Linux KVM SEV initialization allows local attackers to potentially execute code or escalate privileges.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98719, DEBIAN-CVE-2026-98719, GHSA-j294-cf74-gq7q, UBUNTU-CVE-2026-98719

## What is CVE-2026-98719?

CVE-2026-98719 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-98719?


## How do I fix CVE-2026-98719?

Apply the vendor's patch.

## Is CVE-2026-98719 being exploited?

There is no known exploitation of CVE-2026-98719 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98719 and fix it if it is affected.

What it is: CVE-2026-98719 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98719 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98719/ (Markdown: https://insights.sbomify.com/CVE-2026-98719/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98719
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98719
- OSV: https://osv.dev/vulnerability/CVE-2026-98719

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98719/
Summaries are generated and may contain mistakes; the official description above is the record.