# CVE-2026-19676: The user-mode verifier for the peci_transfer() system call, z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the device


- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 21 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** GHSA-g66q-frxm-3hfg

## What is CVE-2026-19676?

CVE-2026-19676 is a high-severity vulnerability in zephyrproject zephyr, published on 21 Oct 2026. 

### Official description

The user-mode verifier for the peci_transfer() system call, z_vrfy_peci_transfer() in drivers/peci/peci_handlers.c, checked only the device object permission and copied the caller-supplied struct peci_msg with k_usermode_from_copy(). That copy validates the outer structure only; the buf pointers and len values inside the embedded struct peci_buf members tx_buffer and rx_buffer remained fully caller-controlled and were passed unchecked to the driver.

Every in-tree PECI driver dereferences those pointers in supervisor mode: peci_npcx_transfer() in drivers/peci/peci_npcx.c and peci_it8xxx2_transfer() in drivers/peci/peci_ite_it8xxx2.c copy hardware bytes into rx_buffer.buf[i] and read command bytes out of tx_buffer.buf[i], and peci_xec_read()/peci_xec_write() in drivers/peci/peci_mchp_xec.c do the same with no bound on rx_buffer.len at all. A user-mode thread that has been granted the PECI device object — the normal way an application exposes a device under CONFIG_USERSPACE — could therefore point rx_buffer.buf at kernel data structures and have the driver write hardware-supplied bytes there, or point tx_buffer.buf at kernel memory and have its contents pushed onto the PECI/eSPI out-of-band bus.

The impact is a full user-mode-to-kernel escape: an arbitrary kernel write primitive (integrity and, through it, code execution at supervisor privilege), an arbitrary kernel read disclosed to a PECI bus observer, and a trivially reachable supervisor-mode fault if an unmapped address is supplied. Exploitation requires CONFIG_USERSPACE=y, one of the PECI drivers enabled (CONFIG_PECI_NPCX, CONFIG_PECI_XEC or CONFIG_PECI_ITE_IT8XXX2), and local code execution in a user-mode thread holding the PECI device.

The fix adds K_SYSCALL_MEMORY_READ() and K_SYSCALL_MEMORY_WRITE() checks over the two embedded buffers, with a size_add_overflow() guard on the frame-check-sequence byte accounted for in the RX length.

Weakness: CWE-822 (Untrusted Pointer Dereference)

## Which versions are affected by CVE-2026-19676?


## How do I fix CVE-2026-19676?

No fix has been published for CVE-2026-19676 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19676 being exploited?

There is no known exploitation of CVE-2026-19676 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19676 and fix it if it is affected.

What it is: CVE-2026-19676 is a high-severity vulnerability in zephyrproject zephyr, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-19676 in the wild and no public exploit code.

Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19676/ (Markdown: https://insights.sbomify.com/CVE-2026-19676/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19676
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19676
- OSV: https://osv.dev/vulnerability/CVE-2026-19676

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19676/
Summaries are generated and may contain mistakes; the official description above is the record.