CVE-2026-93266 arm64: RSI: fix field-spanning write warning in attestation token init

Not scored Published 24 Sep 2026 Updated 19 Oct 2026

A field-spanning write in the Linux kernel arm64 RSI attestation token initialization can trigger a FORTIFY warning and potential kernel panic.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-93266?

CVE-2026-93266 is a memory corruption vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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 &regs.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 "&regs.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

Which versions are affected by CVE-2026-93266?

How do I fix CVE-2026-93266?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-93266 being exploited?

There is no known exploitation of CVE-2026-93266 in the wild and no public exploit code.

Sources

Also known as BELL-CVE-2026-93266, DEBIAN-CVE-2026-93266, GHSA-xvwh-h3f9-mq6w, UBUNTU-CVE-2026-93266.