# CVE-2026-98546: arm64/boot: Disable trapping of PMZR_EL0 writes to EL2

> A local attacker can crash the Linux kernel by writing to PMZR_EL0 when specific performance monitoring configurations are enabled.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98546, DEBIAN-CVE-2026-98546, GHSA-gfjh-3rr5-qgfr, UBUNTU-CVE-2026-98546

## What is CVE-2026-98546?

CVE-2026-98546 is a denial of service 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:

arm64/boot: Disable trapping of PMZR_EL0 writes to EL2

__init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2.
PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in
HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host
traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The
kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU
driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a
write from EL0 reaches the trap and takes the host down without a panic
message.

Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already
does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9
bits.

## Which versions are affected by CVE-2026-98546?


## How do I fix CVE-2026-98546?

Apply the vendor's patch.

## Is CVE-2026-98546 being exploited?

There is no known exploitation of CVE-2026-98546 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98546 and fix it if it is affected.

What it is: CVE-2026-98546 is a denial of service 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-2026-98546 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-2026-98546/ (Markdown: https://insights.sbomify.com/CVE-2026-98546/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98546
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98546
- OSV: https://osv.dev/vulnerability/CVE-2026-98546

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98546/
Summaries are generated and may contain mistakes; the official description above is the record.