Zephyr's Bluetooth Mesh subsystem leaks one PSA Crypto key slot each time a subnet key is torn down because the function that imports the Private Beacon Key into a PSA key slot is not balanced by a corresponding destroy call. The destroy call is guarded by a configuration option (CONFIG_BT_MESH_V1d1) that was removed, making the destroy code permanently dead and never executed. This leak occurs during subnet deletion, key refresh completion, or node reset/re-provisioning. With the default PSA key slot count of 16, after about a dozen add/delete or key refresh cycles, the key slots are exhausted, causing failures in subnet creation and key refresh operations, and potentially starving other PSA crypto consumers until the device is rebooted. The fix involves aligning the destroy guard with the import guard to ensure each key slot is freed properly.

The vulnerability causes a denial of service by exhausting PSA Crypto key slots on the device, which prevents the node from adding new subnets or completing key refresh procedures. This can also affect other PSA crypto operations on the device. The issue requires high privileges (provisioner or network administrator) over the Bluetooth Mesh network to trigger, and does not impact confidentiality or integrity. The CVSS score is 2.4 (low severity).

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, limit the frequency of subnet key deletions and key refresh operations to avoid exhausting PSA key slots. A device reboot temporarily restores functionality by freeing key slots. Monitor vendor channels for an official fix that aligns the destroy guard with the import guard to properly free key slots.