Zephyr up to 4.4.x USB DFU Class usbd_dfu.c handle_download buf null pointer dereference

Summaryinfo

A vulnerability marked as critical has been reported in Zephyr up to 4.4.x. Affected by this issue is the function handle_download of the file subsys/usb/device_next/class/usbd_dfu.c of the component USB DFU Class. Performing a manipulation of the argument buf results in null pointer dereference. This vulnerability was named CVE-2026-12051. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability, which was classified as critical, was found in Zephyr up to 4.4.x. This affects the function handle_download of the file subsys/usb/device_next/class/usbd_dfu.c of the component USB DFU Class. The manipulation of the argument buf with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

The USB DFU class implementation in Zephyr's new (experimental) device_next USB device stack contains a NULL pointer dereference in handle_download() (subsys/usb/device_next/class/usbd_dfu.c). The handler computes MIN(setup->wLength, buf->len) and passes buf->data to the image write callback without checking that the buf net_buf pointer is non-NULL. The handler is reached over the USB control endpoint, driven by the USB host. For a DFU_DNLOAD (download) request with no Data OUT stage — notably the zero-length terminating download that the DFU protocol uses to end a firmware transfer — the USB core invokes the class handler with a NULL buffer. After the device has been advanced to the DFU_DNLOAD_IDLE state (by sending one valid download block and a GET_STATUS), a zero-length DFU_DNLOAD reaches handle_download() with buf == NULL, dereferencing it. The result is a NULL+offset read that triggers a fatal CPU fault, i.e. a denial of service (device crash/reset). The attacker is whatever controls the USB host the device is attached to; DFU download support must be enabled with a registered image. There is no memory corruption or information disclosure — impact is limited to availability. The fix adds an explicit if (buf != NULL) guard so the callback receives a zero-length, NULL-data transfer instead of crashing.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-12051 since 06/12/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available.

Upgrading to version 4.5.0 eliminates this vulnerability. Applying the patch 552ca371257597b71490482d5cc597157ea60f12 is able to eliminate this problem.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• Zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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