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.
Affected products
zephyrproject: zephyr
References2
- github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-2… ExploitPatchVendor Advisory
- github.com/zephyrproject-rtos/zephyr/commit/c7292f20223637232b6… Patch
Metrics
- CVSS 3.1
-
7.6
HIGH
Score source: CNA
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H - EPSS — exploit probability
- 0% percentile: 23 · as of 13 November 2026
- CWE
- CWE-416
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