# CVE-2026-99017: riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE


- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** BELL-CVE-2026-99017, DEBIAN-CVE-2026-99017, GHSA-67f9-vvv7-wpq7, UBUNTU-CVE-2026-99017

## What is CVE-2026-99017?

CVE-2026-99017 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE

errata_probe_ghostwrite() only marks the CPU as vulnerable when it is
called at the RISCV_ALTERNATIVES_EARLY_BOOT stage, and the mitigation
in ghostwrite_enable_mitigation() only takes effect if the vulnerable
state was recorded before the boot alternatives are patched.

The early boot stage is only executed when CONFIG_RISCV_ALTERNATIVE_EARLY
is enabled, which currently is only selected by ERRATA_THEAD_MAE. In a
kernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n, the
early alternatives never run, so ghostwrite_state is never set to
VULNERABLE: ghostwrite_enable_mitigation() returns false, xtheadvector
remains enabled, and sysfs reports "Not affected" on a vulnerable
T-Head C9xx CPU.

Select RISCV_ALTERNATIVE_EARLY from ERRATA_THEAD_GHOSTWRITE so that the
vulnerability is detected in the early boot stage and the default
mitigation is applied.

## Which versions are affected by CVE-2026-99017?


## How do I fix CVE-2026-99017?

Upgrade to a fixed version.

## Is CVE-2026-99017 being exploited?

There is no known exploitation of CVE-2026-99017 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99017 and fix it if it is affected.

What it is: CVE-2026-99017 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99017 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-2026-99017/ (Markdown: https://insights.sbomify.com/CVE-2026-99017/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99017
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99017
- OSV: https://osv.dev/vulnerability/CVE-2026-99017

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99017/
Summaries are generated and may contain mistakes; the official description above is the record.