CVE-2026-14366: SiWx91x WiFi driver double-unref / use-after-free of caller-owned TX net_pkt
The Silicon Labs SiWx917 WiFi driver's transmit callback siwx91xsend() in drivers/wifi/siwx91x/siwx91xwifi.c frees a network packet it does not own. In the Zephyr TX path the netpkt is owned by the L2/networking stack; the driver only borrows it to copy the frame bytes into a local netbuf. Before the fix, after transmitting, siwx91xsend() additionally called netpktunref(pkt) on the caller-owned packet, dropping its last reference and returning it to the shared packet pool prematurely. This code path is compiled in by default (CONFIGWIFISILABSSIWX91XNETSTACKNATIVE).
The caller, ethernetsend() in subsys/net/l2/ethernet/ethernet.c, keeps using the packet after the driver returns: it reads netpktgetlen(pkt), updates TX statistics, and then performs its own netpktunref(pkt). Because the driver already released the packet, these are use-after-free reads followed by a second unref (a double free). When concurrent network activity recycles the freed slab slot between the two unrefs, the trailing unref decrements a different, live packet's reference count and frees it, corrupting the netpkt pool shared by both the receive and transmit paths.
The defect is exercised by ordinary transmission over the native-stack SiWx917 WiFi interface, and an adjacent attacker on the same WiFi network can induce transmissions (for example ARP or ICMP echo replies, or TCP handshakes) to drive the path. The primary observable impact is loss of availability (transmit hangs and crashes from pool corruption), with race-dependent memory corruption of the kernel networking buffer pool. The fix removes the erroneous netpktunref(pkt) from siwx91xsend(); the driver's receive-path unref, which correctly frees a packet the driver itself allocated, is unaffected.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Fix the transmit callback siwx91x_send() by removing the erroneous net_pkt_unref(pkt) that drops the caller-owned packet's last reference; the driver should only borrow the TX net_pkt and unref only packets it allocated itself.
Zephyr SiWx917 WiFi driver (drivers/wifi/siwx91x/siwx91x_wifi.c) net_pkt_unref() call in siwx91x_send() = remove erroneous net_pkt_unref on caller-owned TX net_pkt
Event History
Frequently Asked Questions
Is a default build affected?
Yes. The vulnerable code path is compiled in by default through CONFIG_WIFI_SILABS_SIWX91X_NET_STACK_NATIVE.
What level of attacker access is required?
The CVSS vector identifies adjacent-network attack access, with no privileges or user interaction required. Exploitation is rated high complexity.
Can the issue affect traffic beyond the packet being transmitted?
Yes. If a freed packet-pool slot is recycled during concurrent network activity, the later unref can target a different live packet. This can corrupt the shared net_pkt pool used by both receive and transmit paths.