---
title: "CVE-2026-99018: Linux Kernel - Broken Access Control"
description: "Linux kernel contains a broken access control vulnerability caused by improper determination of user mode entry using tp register instead of sstatus.SPP bit in riscv entry, letting unprivileged attackers achieve arbitrary kernel write and control-flow hijack, exploit requires CONFIG_SHADOW_CALL_STACK enabled."
url: https://panop.io/threat-heartbeat/CVE-2026-99018/
---

# CVE-2026-99018 Linux Kernel - Broken Access Control

Linux kernel contains a broken access control vulnerability caused by improper determination of user mode entry using tp register instead of sstatus.SPP bit in riscv entry, letting unprivileged attackers achieve arbitrary kernel write and control-flow hijack, exploit requires CONFIG\_SHADOW\_CALL\_STACK enabled.

CVSS base score 7.8 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.21% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-99018)

## Details

Type

Broken Access Control

Impact

Data Tampering

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Published

23 October 2026

Updated

25 October 2026

## Vendor fix

Update to the latest Linux kernel version containing the fix.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-99018](https://nvd.nist.gov/vuln/detail/CVE-2026-99018)
- [https://git.kernel.org/stable/c/37b4401ee6fa06046446d55e97e8d11784080843](https://git.kernel.org/stable/c/37b4401ee6fa06046446d55e97e8d11784080843)
- [https://git.kernel.org/stable/c/4d0697f192975dab5985e921989be1d85cf580e9](https://git.kernel.org/stable/c/4d0697f192975dab5985e921989be1d85cf580e9)
- [https://git.kernel.org/stable/c/6639735367a7d491977e9e5e7afc50b489d81d83](https://git.kernel.org/stable/c/6639735367a7d491977e9e5e7afc50b489d81d83)
- [https://git.kernel.org/stable/c/7d1367a53137e379498eb8791295e58854378636](https://git.kernel.org/stable/c/7d1367a53137e379498eb8791295e58854378636)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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