# CVE-2026-89436: platform/x86: panasonic-laptop: Fix sentinel write past pcc->sinf[]

> A heap buffer overflow in the panasonic-laptop kernel driver allows attackers to corrupt memory, potentially leading to code execution or privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** GHSA-j34j-9955-32cv, UBUNTU-CVE-2026-89436

## What is CVE-2026-89436?

CVE-2026-89436 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: panasonic-laptop: Fix sentinel write past pcc->sinf[]

acpi_pcc_retrieve_biosdata() rejects SINF packages only when
pcc->num_sifr is strictly less than hkey->package.count, then
unconditionally writes a trailing sentinel at
pcc->sinf[hkey->package.count]. But pcc->sinf[] is allocated with
exactly pcc->num_sifr elements (valid indices 0..num_sifr-1), so that
write needs num_sifr strictly greater than package.count to stay in
bounds -- num_sifr == package.count passes the existing check but
still overflows by one element.

This is exactly the case probe()'s existing num_sifr++ workaround
("Some DSDT-s have an off-by-one bug where the SINF package count is
one higher than the SQTY reported value") is written to accommodate:
when a DSDT's SINF package count equals SQTY+1, the workaround makes
num_sifr equal to package.count, which is precisely the boundary that
overflows here. Found via UBSan (array-index-out-of-bounds) on
hardware where HKEY.SQTY returns 37 and HKEY.SINF()'s package has 38
elements: num_sifr becomes 38 after the += 1 workaround, the loop
correctly fills indices 0..37, and the sentinel write then targets
index 38, one past the end -- a silent 4-byte heap overflow on kernels
without CONFIG_UBSAN.

Tightening the rejection check to num_sifr <= package.count would
avoid the overflow but breaks probe() entirely on exactly this
hardware, since num_sifr == package.count is the case the off-by-one
workaround exists to support. Nothing else in the driver reads this
sentinel value back, so simply skip the write when there is no room
for it instead.

## Which versions are affected by CVE-2026-89436?


## How do I fix CVE-2026-89436?

Apply the vendor's patch.

## Is CVE-2026-89436 being exploited?

There is no known exploitation of CVE-2026-89436 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89436 and fix it if it is affected.

What it is: CVE-2026-89436 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-2026-89436 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-2026-89436/ (Markdown: https://insights.sbomify.com/CVE-2026-89436/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89436
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89436
- OSV: https://osv.dev/vulnerability/CVE-2026-89436

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89436/
Summaries are generated and may contain mistakes; the official description above is the record.