# CVE-2026-19570: Out-of-bounds write in LE Audio Broadcast Sink when copying BASE subgroup metadata into the BASS receive state

> An attacker in radio range can trigger an out-of-bounds write in Zephyr's LE Audio Broadcast Sink, potentially leading to code execution or denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/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:** 9 Oct 2026
- **Updated:** 9 Oct 2026
- **Also known as:** GHSA-4qwc-2qfq-w2fj

## What is CVE-2026-19570?

CVE-2026-19570 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 9 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The LE Audio Broadcast Sink in subsys/bluetooth/audio/bap_broadcast_sink.c copies subgroup metadata from a received Basic Audio Announcement (BASE) into the static Broadcast Audio Scan Service parameter structure mod_src_param without any bounds check. In base_subgroup_meta_cb() the destination element was selected as mod_src_param.subgroups[mod_src_param.num_subgroups] with no test against ARRAY_SIZE(mod_src_param.subgroups) (sized by CONFIG_BT_BAP_BASS_MAX_SUBGROUPS, default 1), and the metadata was copied with memcpy() using the raw on-air length returned by bt_bap_base_get_subgroup_codec_meta() into a metadata array sized by CONFIG_BT_AUDIO_CODEC_CFG_MAX_METADATA_SIZE (default 4). The BASE validator bt_bap_base_get_base_from_ad() only checks structural consistency and permits up to ~24 subgroups and metadata LTVs of ~240 octets.

The defect is reached from the periodic advertising receive callback: pa_recv() → bt_data_parse() → pa_decode_base() → update_recv_state_base() → bt_bap_base_foreach_subgroup() → base_subgroup_meta_cb(). Every broadcast sink registers a scan-delegator receive state at creation (bt_bap_broadcast_sink_create() calls broadcast_sink_add_src()), and CONFIG_BT_BAP_BROADCAST_SINK depends on CONFIG_BT_BAP_SCAN_DELEGATOR, so the path is active in every broadcast-sink build once the device is periodic-advertising-synced. An attacker in radio range who operates a broadcast source the device syncs to — or who impersonates the advertiser address and SID of one already in use, periodic advertising data being unauthenticated — can change the BASE at will; each new BASE is re-parsed.

A crafted BASE therefore writes attacker-chosen bytes past the end of a fixed static object in .bss: up to roughly 236 bytes for an oversized metadata LTV, plus whole struct bt_bap_bass_subgroup records for each subgroup beyond CONFIG_BT_BAP_BASS_MAX_SUBGROUPS. This is memory corruption of adjacent Bluetooth-audio state reachable with no pairing, bonding or GATT connection, with a potential for remote code execution in the Bluetooth RX thread; in addition, the unvalidated metadata_len is forwarded to bt_bap_scan_delegator_mod_src(), which neither clamps it nor rejects it, leading to a further copy into the receive state and to out-of-bounds memory being disclosed in the BASS receive-state notification sent to a connected Broadcast Assistant.

The fix rejects a BASE carrying more subgroups than the receive state can hold (discarding the update entirely) and omits metadata that does not fit rather than copying it, and additionally honours the previously-ignored error return of the subgroup decode pass.

Weakness: CWE-787 (Out-of-bounds Write), CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2026-19570?


## How do I fix CVE-2026-19570?

No fix has been published for CVE-2026-19570 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19570 being exploited?

There is no known exploitation of CVE-2026-19570 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19570 and fix it if it is affected.

What it is: CVE-2026-19570 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 9 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-2026-19570 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-2026-19570/ (Markdown: https://insights.sbomify.com/CVE-2026-19570/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19570
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19570
- OSV: https://osv.dev/vulnerability/CVE-2026-19570

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-19570/
Summaries are generated and may contain mistakes; the official description above is the record.