# CVE-2026-19185: Memory corruption in zephyr

> Unvalidated pointers in the I3C system call allow user-mode threads to read or write arbitrary kernel memory, leading to privilege escalation.

- **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
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Oct 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-pcrr-29j7-8w57

## What is CVE-2026-19185?

CVE-2026-19185 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 5 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.

The defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.

A read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.

The fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.

Weakness: CWE-822 (Untrusted Pointer Dereference)

## Which versions are affected by CVE-2026-19185?


## How do I fix CVE-2026-19185?

No fix has been published for CVE-2026-19185 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19185 being exploited?

There is no known exploitation of CVE-2026-19185 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19185 and fix it if it is affected.

What it is: CVE-2026-19185 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 5 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-19185 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-2026-19185/ (Markdown: https://insights.sbomify.com/CVE-2026-19185/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19185
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19185
- OSV: https://osv.dev/vulnerability/CVE-2026-19185

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19185/
Summaries are generated and may contain mistakes; the official description above is the record.