# CVE-2026-10685: Use-after-free of GATT subscribe params in Bluetooth host CCC-write response handler

> A use-after-free in Zephyr's Bluetooth GATT client allows remote attackers to cause crashes or execute code via crafted ATT error responses.

- **Severity:** High 7.6 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:** 31 Jul 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-29xh-jm2m-4qvx

## What is CVE-2026-10685?

CVE-2026-10685 is a high-severity use after free vulnerability in Zephyrproject Zephyr, published on 31 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The Zephyr Bluetooth GATT client CCC-write response handler gatt_write_ccc_rsp() in subsys/bluetooth/host/gatt.c invoked the application's params->subscribe() callback after it had already called params->notify(conn, params, NULL, 0).

Per the public GATT API, a notify callback with NULL data is the documented signal that the subscription has terminated and the bt_gatt_subscribe_params struct may be freed or reused by the application; calling subscribe() on the struct afterwards is a use-after-free, including an indirect call through the freed params->subscribe function pointer.

The error branch is remotely (adjacent) reachable: a Zephyr device acting as a GATT client that calls bt_gatt_subscribe() can be driven into this ordering when a connected GATT server peer answers the CCC write with an ATT Error Response (the peer-supplied error code flows through att_error_rsp -> att_handle_rsp into gatt_write_ccc_rsp).

For applications that free or recycle subscription parameters in their notification-termination handler, this results in memory corruption, a crash (denial of service), or potentially attacker-influenced control flow. The fix reorders the handler so the subscribe() callback runs before the terminating notify(NULL) in both the error and unsubscribe paths.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-10685?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2026-10685?

No fix has been published for CVE-2026-10685 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10685 being exploited?

There is no known exploitation of CVE-2026-10685 in the wild and no public exploit code.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2026-5067](https://insights.sbomify.com/CVE-2026-5067/): Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key (critical 9.8)
- [CVE-2022-3806](https://insights.sbomify.com/CVE-2022-3806/): Bluetooth HCI Error Handling Double Free (critical 9.8)
- [CVE-2017-14199](https://insights.sbomify.com/CVE-2017-14199/): Memory corruption in getaddrinfo (critical 9.8)
- [CVE-2018-1000800](https://insights.sbomify.com/CVE-2018-1000800/): Null dereference in n/a (critical 9.8)
- [CVE-2021-3329](https://insights.sbomify.com/CVE-2021-3329/): DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-10685 and fix it if it is affected.

What it is: CVE-2026-10685 is a high-severity use after free vulnerability in Zephyrproject Zephyr, published on 31 Jul 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-2026-10685 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-2026-10685/ (Markdown: https://insights.sbomify.com/CVE-2026-10685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10685
- OSV: https://osv.dev/vulnerability/CVE-2026-10685

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-10685/
Summaries are generated and may contain mistakes; the official description above is the record.