# CVE-2026-89443: platform/x86: ISST: Validate level in perf mask ioctls

> A missing bounds check in the Linux kernel ISST driver allows local attackers to trigger out-of-bounds reads via crafted ioctl calls, potentially leaking memory or causing crashes.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100518, BELL-CVE-2026-89443, DEBIAN-CVE-2026-89443, GHSA-5hf2-3p4g-qfhr, UBUNTU-CVE-2026-89443

## What is CVE-2026-89443?

CVE-2026-89443 is a high-severity memory corruption vulnerability in Linux, published on 11 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:

platform/x86: ISST: Validate level in perf mask ioctls

isst_if_get_perf_level_mask() and isst_if_get_base_freq_mask() use the
user-provided level as an index into perf_levels[] via
_read_pp_level_info() and _read_bf_level_info(), but neither helper
validates it first.

The adjacent level-info helpers reject levels above max_level before
reading the same per-level register block. Add the same bounds checks to
the mask helpers, and reject disabled SST-PP levels in
isst_if_get_perf_level_mask() to match isst_if_get_perf_level_info().

This prevents out-of-bounds reads from the per-level offset table on
invalid ioctl input.

## Which versions are affected by CVE-2026-89443?


## How do I fix CVE-2026-89443?

Apply the vendor's patch.

## Is CVE-2026-89443 being exploited?

There is no known exploitation of CVE-2026-89443 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89443 and fix it if it is affected.

What it is: CVE-2026-89443 is a high-severity memory corruption vulnerability in Linux, published on 11 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-2026-89443 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-2026-89443/ (Markdown: https://insights.sbomify.com/CVE-2026-89443/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89443
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89443
- OSV: https://osv.dev/vulnerability/CVE-2026-89443

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89443/
Summaries are generated and may contain mistakes; the official description above is the record.