# CVE-2026-14986: Out-of-bounds write in it51xxx I2C target FIFO ISR on oversized write transaction

> An out-of-bounds write in the ITE I2C driver allows a malicious I2C master to corrupt memory, potentially leading to code execution or denial of service.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** GHSA-jmjj-w736-fw2j

## What is CVE-2026-14986?

CVE-2026-14986 is a medium-severity memory corruption vulnerability in zephyrproject zephyr, published on 14 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The ITE it51xxx I2C driver, when operating as an I2C target (slave) in buffer mode (CONFIG_I2C_TARGET + CONFIG_I2C_TARGET_BUFFER_MODE), copies host-supplied write data into the fixed-size data->target_in_buffer inside its target FIFO interrupt handler target_i2c_isr_fifo() in drivers/i2c/i2c_ite_it51xxx.c. The copy loop stores to target_in_buffer[i + data->w_index] and only checks data->w_index against sizeof(data->target_in_buffer) after the write has already completed, so the bounds check cannot prevent the overflow.

The running index data->w_index accumulates count bytes on every FIFO-fill interrupt of an ongoing transaction and is reset to zero only on a STOP or timeout condition. An I2C host that streams a single write transaction longer than the buffer (default CONFIG_I2C_TARGET_IT51XXX_MAX_BUF_SIZE = 256 bytes) drives data->w_index past the end of the buffer, and each subsequent host byte is written out of bounds into the adjacent data->target_out_buffer and following static device data.

The trigger is a malicious or misbehaving I2C master on the same bus (for example a compromised application processor or a rogue device on an exposed I2C bus); no software privilege on the victim is required and the handler runs in the target's kernel/firmware context. Because both the written values and the overflow length are attacker-controlled, this is an out-of-bounds write that can crash the controller or be shaped toward code execution. The fix adds a pre-write bounds check in target_i2c_fifo_read_to_buf() that aborts and resets the FIFO before any out-of-bounds store.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-14986?


## How do I fix CVE-2026-14986?

No fix has been published for CVE-2026-14986 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-14986 being exploited?

There is no known exploitation of CVE-2026-14986 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-14986 and fix it if it is affected.

What it is: CVE-2026-14986 is a medium-severity memory corruption vulnerability in zephyrproject zephyr, published on 14 Sep 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-2026-14986 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-2026-14986/ (Markdown: https://insights.sbomify.com/CVE-2026-14986/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-14986
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-14986
- OSV: https://osv.dev/vulnerability/CVE-2026-14986

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-14986/
Summaries are generated and may contain mistakes; the official description above is the record.