---
id: CVE-2026-9263
title: >-
  Out-of-bounds read in Bluetooth Controller ISOAL framed RX reassembly leaks
  adjacent memory into host HCI ISO packets
summary: >-
  The Zephyr Bluetooth controller ISO Adaptation Layer
  (subsys/bluetooth/controller/ll_sw/isoal.c) fails to validate the length field
  of a framed ISO PDU start segment. Per the Bluetooth specification a start
  segment (sc=0) always carries …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cvssSource: cna
cwe:
  - CWE-125
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 3.3.0 < 4.3.1
  - zephyr >= 4.4.0 < 4.4.1
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-06-30T16:40:19.038346Z'
exploitAvailable: true
published: '2026-06-30'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:29.298Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-9263'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/28080d80fc8aca30af1dfd1338bd4481b13c7395
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-6gvp-pmh8-fjh2
    label: GHSA-6gvp-pmh8-fjh2
tags:
  - cve.org
  - exploit-available
epss: 0.00327
epssPercentile: 0.24137
ingestedAt: '2026-10-15T22:48:25.576Z'
---

## Overview

The Zephyr Bluetooth controller ISO Adaptation Layer (subsys/bluetooth/controller/ll_sw/isoal.c) fails to validate the length field of a framed ISO PDU start segment. Per the Bluetooth specification a start segment (sc=0) always carries a 3-byte time_offset, so its segment-header len must be at least PDU_ISO_SEG_TIMEOFFSET_SIZE (3). isoal_check_seg_header() accepted start segments with len < 3 as valid, and isoal_rx_framed_consume() then computed length = seg_hdr->len - 3 in a uint8_t, underflowing to 253-255 when len is 0-2. That oversized length is passed to isoal_rx_append_to_sdu(), whose copy is clamped only against the destination SDU buffer size, not the source PDU length, so up to ~255 bytes of controller memory beyond the received PDU are copied (via sink_sdu_write_hci()/net_buf_add_mem) into an HCI ISO data packet and delivered to the host. The PDU and its segment headers are entirely attacker-controlled and arrive over the air, reachable through both the CIS and BIS-sync HCI data paths (hci_driver.c) and the vendor data path (ull_iso.c), so a remote CIS peer or a broadcaster the device is synced to can trigger an out-of-bounds read causing information disclosure to the host and potential denial of service (faults or malformed oversized HCI ISO packets). The flaw affects all Zephyr releases since framed ISO reception was introduced in v3.0.0. The fix rejects sc=0 segments with len < 3 in isoal_check_seg_header() and adds a guard before the subtraction in isoal_rx_framed_consume().

## Affected

- `zephyr >= 3.3.0 < 4.3.1`
- `zephyr >= 4.4.0 < 4.4.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.