# CVE-2026-19186: Integer underflow in IEEE 802.15.4 frame decryption leads to out-of-bounds read and write


- **Severity:** High 8.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 7 Oct 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-6x64-rwq6-j8x3

## What is CVE-2026-19186?

CVE-2026-19186 is a high-severity vulnerability in zephyrproject zephyr, published on 7 Oct 2026. 

### Official description

ieee802154_decipher_data_frame() in subsys/net/l2/ieee802154/ieee802154_frame.c computed payload_len = net_pkt_get_len(pkt) - ll_hdr_len - authtag_len without first checking that the received frame is at least ll_hdr_len + authtag_len bytes long. All three variables are uint8_t, so a frame whose payload is shorter than the configured authentication tag makes the subtraction wrap around to a large value (up to 255).

The wrapped length is passed unchanged to ieee802154_decrypt_auth() and on to the CCM operation as cipher_pkt.in_len/out_buf_max, with apkt->tag pointing at frame + ll_hdr_len + payload_len. Because the receive buffer is allocated to the exact length of the frame received from the radio driver, the crypto layer then reads several hundred bytes past the end of the packet buffer and writes the same number of decrypted bytes back over it in place. The frame's authentication tag is only verified after this processing has taken place, so no key material, association or prior authentication is needed — a single crafted short frame from any device in radio range is sufficient. Frame validation in ieee802154_validate_frame() does not prevent it: a data frame is accepted with a one-byte payload.

The result is an out-of-bounds read and an out-of-bounds write of up to roughly 240 bytes into the adjacent network-buffer pool, corrupting other packets or allocator metadata and typically faulting the target. The out-of-bounds content is not attacker-chosen (it is ciphertext XOR keystream over out-of-bounds memory) and the frame is dropped when tag verification fails, so the primary impact is memory corruption and denial of service rather than information disclosure.

Exposure is limited to configurations that enable the experimental CONFIG_NET_L2_IEEE802154_SECURITY option, select a crypto device via CONFIG_NET_L2_IEEE802154_SECURITY_CRYPTO_DEV_NAME, and have established a security session with a level other than IEEE802154_SECURITY_LEVEL_NONE; with security disabled or at level NONE the tag length is zero and no underflow occurs. The fix rejects frames shorter than ll_hdr_len + authtag_len before the subtraction, and adds the matching guard on the transmit side in ieee802154_create_data_frame().

Weakness: CWE-787 (Out-of-bounds Write), CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-19186?


## How do I fix CVE-2026-19186?

No fix has been published for CVE-2026-19186 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19186 being exploited?

There is no known exploitation of CVE-2026-19186 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19186 and fix it if it is affected.

What it is: CVE-2026-19186 is a high-severity vulnerability in zephyrproject zephyr, published on 7 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-19186 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-2026-19186/ (Markdown: https://insights.sbomify.com/CVE-2026-19186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19186
- OSV: https://osv.dev/vulnerability/CVE-2026-19186

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19186/
Summaries are generated and may contain mistakes; the official description above is the record.