CVE-2026-9263 Out-of-bounds read in Bluetooth Controller ISOAL framed RX reassembly leaks adjacent memory into host HCI ISO packets

What is CVE-2026-9263?

CVE-2026-9263 is a medium-severity vulnerability in Zephyrproject Zephyr, published on 30 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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().

Weakness: CWE-125

Which versions are affected by CVE-2026-9263?

It affects 1 product.

Products include Zephyrproject Zephyr.

How do I fix CVE-2026-9263?

No fix has been published for CVE-2026-9263 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-9263 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-9263 exists.

Other vulnerabilities in Zephyrproject Zephyr

• 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 Bluetooth HCI Error Handling Double Free Critical 9.8
• CVE-2017-14199 Memory corruption in getaddrinfo Critical 9.8
• CVE-2018-1000800 Null dereference in n/a Critical 9.8
• CVE-2021-3329 DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer Critical 9.6

All Zephyrproject Zephyr vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-6gvp-pmh8-fjh2.