zephyrproject zephyr up to 4.4.x isoal.c isoal_check_seg_header length out-of-bounds

Summaryinfo

A vulnerability classified as problematic was found in zephyrproject zephyr up to 4.4.x. This impacts the function isoal_check_seg_header of the file subsys/bluetooth/controller/ll_sw/isoal.c. Executing a manipulation of the argument length can lead to out-of-bounds. This vulnerability appears as CVE-2026-9263. The attacker needs to be present on the local network. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic was found in zephyrproject zephyr up to 4.4.x. This vulnerability affects the function isoal_check_seg_header of the file subsys/bluetooth/controller/ll_sw/isoal.c. The manipulation of the argument length with an unknown input leads to a out-of-bounds vulnerability. The CWE definition for the vulnerability is CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality. CVE summarizes:

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 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().

The advisory is available at github.com. This vulnerability was named CVE-2026-9263 since 05/22/2026. The exploitation appears to be easy. The attack needs to approached within the local network. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 4.5.0 eliminates this vulnerability. Applying the patch 28080d80fc8aca30af1dfd1338bd4481b13c7395 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Project Management Software

Vendor

• zephyrproject

Name

• zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

License

• open-source

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CPE 2.2info

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