CVE-2026-93266

Overview

CVE-2026-93266 is a high‑severity kernel bug on ARM64 that causes a field‑spanning write during attestation token initialization. The flaw can corrupt kernel memory, potentially leading to privilege escalation or denial of service. It affects any system running the vulnerable Linux kernel on ARM64 platforms.

Description

In the Linux kernel, the following vulnerability has been resolved: arm64: RSI: fix field-spanning write warning in attestation token init The challenge is passed in registers a1 through a8. However, copying to ®s.a1 makes FORTIFY treat the destination as the single a1 field, resulting in a field-spanning write warning. [1] Overlay the SMCCC register structure with an RSI-specific argument layout and copy the challenge into an explicit 64-byte array. This keeps the existing a1-a8 argument encoding while giving the copy a correctly sized destination object. [1] memcpy: detected field-spanning write (size 64) of single field "®s.a1" at ./arch/arm64/include/asm/rsi_cmds.h:119 (size 8) WARNING: ./arch/arm64/include/asm/rsi_cmds.h:119 at rsi_attestation_token_init+0xdc/0xf8 [arm_cca_guest], CPU#0: cat/3314

Impact

The vulnerability can compromise confidentiality, integrity, and availability of the operating system by corrupting kernel memory. Privileged processes and users on affected systems are at risk of privilege escalation or service disruption.

Remediation

Update the kernel to a version that includes the RSI attestation token init fix. Verify the kernel version with "uname -r" and apply the vendor’s security update or backport the patch. If an update is not immediately possible, disable RSI or attestation features via kernel boot parameters or configuration options, and monitor system logs for related warnings.

Risk context

The CVSS v3 score of 7.1 and high severity indicate a significant risk. While no EPSS data is available, the flaw warrants prompt patching to mitigate potential exploitation.

Affected products

• Linux kernel arm64
• Ubuntu 24.04 arm64
• RedHat Enterprise Linux 9 arm64
• CentOS Stream 9 arm64
• Fedora 40 arm64
• SUSE Linux Enterprise Server 15 arm64
• Debian 12 arm64
• Raspberry Pi OS arm64