# CVE-2026-72292: KVM: s390: Initialize KVM_S390_GET_CMMA_BITS memory

> A local attacker with KVM access can read uninitialized kernel memory via the KVM_S390_GET_CMMA_BITS ioctl due to missing buffer initialization.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72292, GHSA-g39r-65h4-wx32, UBUNTU-CVE-2026-72292

## What is CVE-2026-72292?

CVE-2026-72292 is a vulnerability in Linux, published on 15 Aug 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: s390: Initialize KVM_S390_GET_CMMA_BITS memory

kvm_s390_get_cmma_bits() allocates its output buffer with vmalloc(),
which does not zero the returned pages:

	values = vmalloc(args->count);

In the non-peek (migration) path, dat_get_cmma() reports a byte count
spanning from the first to the last dirty page, but __dat_get_cmma_pte()
writes values[gfn - start] only for pages whose CMMA dirty bit is set.
The walk uses DAT_WALK_IGN_HOLES, so clean and unmapped pages that lie
between two dirty pages within the reported span are visited but never
store their byte.  Those gaps (up to KVM_S390_MAX_BIT_DISTANCE pages
each) stay uninitialized yet fall inside [0, count) and are copied out
by copy_to_user(), disclosing stale kernel memory to user space.

Before the switch to the new gmap implementation the buffer was fully
populated for every gfn in the span, so no uninitialized bytes were
exposed; the dirty-only walk introduced the leak.

Use vzalloc() so the gaps read back as zero.

## Which versions are affected by CVE-2026-72292?


## How do I fix CVE-2026-72292?

Apply the vendor's patch.

## Is CVE-2026-72292 being exploited?

There is no known exploitation of CVE-2026-72292 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72292 and fix it if it is affected.

What it is: CVE-2026-72292 is a vulnerability in Linux, published on 15 Aug 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-2026-72292 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-2026-72292/ (Markdown: https://insights.sbomify.com/CVE-2026-72292/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72292
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72292
- OSV: https://osv.dev/vulnerability/CVE-2026-72292

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72292/
Summaries are generated and may contain mistakes; the official description above is the record.