# CVE-2026-90272: perf: arm_pmuv3: Zero initialize hw_id branch stack field

> A local attacker can read uninitialized kernel memory via the ARM PMU branch stack interface, potentially exposing sensitive data.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90272, DEBIAN-CVE-2026-90272, GHSA-8j89-gr3p-jpp8, UBUNTU-CVE-2026-90272

## What is CVE-2026-90272?

CVE-2026-90272 is a vulnerability in Linux, published on 17 Sep 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:

perf: arm_pmuv3: Zero initialize hw_id branch stack field

PERF_SAMPLE_BRANCH_HW_INDEX is supported by BRBE so hw_id is passed to
userspace, but it's never set by the BRBE driver. Zero initialize it as
it should be according to the docs:

   * For the architectures whose raw branch records are
   * already stored in age order, the hw_idx should be 0.

It's probably too risky to remove PERF_SAMPLE_BRANCH_HW_INDEX from BRBE
now in case anyone is setting it and reading the value, but zero
initializing the whole struct also protects against the same issue with
new fields that are added in the future.

## Which versions are affected by CVE-2026-90272?


## How do I fix CVE-2026-90272?

Apply the vendor's patch.

## Is CVE-2026-90272 being exploited?

There is no known exploitation of CVE-2026-90272 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90272 and fix it if it is affected.

What it is: CVE-2026-90272 is a vulnerability in Linux, published on 17 Sep 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-2026-90272 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-2026-90272/ (Markdown: https://insights.sbomify.com/CVE-2026-90272/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90272
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90272
- OSV: https://osv.dev/vulnerability/CVE-2026-90272

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90272/
Summaries are generated and may contain mistakes; the official description above is the record.