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

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.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-99017, DEBIAN-CVE-2026-99017, GHSA-67f9-vvv7-wpq7, UBUNTU-CVE-2026-99017.