# CVE-2026-99017: Linux kernel T-Head ghostwrite detection bypass in RISC-V errata

Source: https://junglewise.ai/threats/cve-2026-99017-in-the-linux-kernel-the-following-vulnerability-has-been-resolved  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-99017 · Severity: info · Published 2026-10-23

The Linux kernel's RISC-V errata handling failed to detect a T-Head C9xx CPU vulnerability (ghostwrite) when certain configuration options were disabled. On vulnerable systems, the kernel would incorrectly report the CPU as not affected and leave the xtheadvector extension enabled, removing the intended protection against the vulnerability.

Technologies: [Linux kernel](https://junglewise.ai/threats/technologies/x-linux-kernel).

## Quick answers

**Is CVE-2026-99017 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-99017 being exploited in the wild.

**How severe is CVE-2026-99017?** Informational severity, published 23 October 2026.

**Which products and versions are affected?** Linux kernel kernels with ERRATA_THEAD_GHOSTWRITE enabled but ERRATA_THEAD_MAE disabled.

**Is there a fix for CVE-2026-99017?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-99017 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-99017?** Check whether you run Linux kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This is a logic error in the kernel's errata detection mechanism for RISC-V. The vulnerability detection function errata_probe_ghostwrite() only executes during early boot when CONFIG_RISCV_ALTERNATIVE_EARLY is enabled, but this config was only selected by ERRATA_THEAD_MAE. A kernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n would skip the early alternatives stage, leaving the vulnerable xtheadvector extension enabled and the kernel reporting "Not affected" on T-Head C9xx CPUs. The fix ensures CONFIG_RISCV_ALTERNATIVE_EARLY is always selected when ghostwrite errata handling is enabled.

## Affected products

- Linux kernel kernels with ERRATA_THEAD_GHOSTWRITE enabled but ERRATA_THEAD_MAE disabled

## Timeline

- 2026-10-23: disclosed

## References

- [https://git.kernel.org/stable/c/298510bbc7c3017c0faf481c6ea66f1065b657b4](https://git.kernel.org/stable/c/298510bbc7c3017c0faf481c6ea66f1065b657b4)
- [https://git.kernel.org/stable/c/7fee577a2fa78b9a76da015beec1ccf978746ebb](https://git.kernel.org/stable/c/7fee577a2fa78b9a76da015beec1ccf978746ebb)

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