Zephyr 4.2.0 (Working Draft)

We are pleased to announce the release of Zephyr version 4.2.0.

Major enhancements with this release include:

An overview of the changes required or recommended when migrating your application from Zephyr v4.1.0 to Zephyr v4.2.0 can be found in the separate migration guide.

The following sections provide detailed lists of changes by component.

Security Vulnerability Related

The following CVEs are addressed by this release:

• CVE 2025-27809 TLS clients may unwittingly skip server authentication

• CVE 2025-27810 Potential authentication bypass in TLS handshake

• CVE 2025-2962 Under embargo until 2025-06-07

More detailed information can be found in: https://docs.zephyrproject.org/latest/security/vulnerabilities.html

API Changes

Removed APIs and options

• Removed the deprecated the net_buf_put() and net_buf_get() API functions.

• Removed the deprecated include/zephyr/net/buf.h header file.

• Removed the --disable-unrecognized-section-test Twister option. Test has been removed and the option became the default behavior.

• Removed the deprecated kscan subsystem.

• Removed meas,ms5837 and replaced with meas,ms5837-30ba and meas,ms5837-02ba.

• Removed the get_ctrl video driver API

Deprecated APIs and options

• The scheduler Kconfig options CONFIG_SCHED_DUMB and CONFIG_WAITQ_DUMB were renamed and deprecated. Use CONFIG_SCHED_SIMPLE and CONFIG_WAITQ_SIMPLE instead.

• The CONFIG_LWM2M_ENGINE_MESSAGE_HEADER_SIZE Kconfig option has been removed. The required header size should be included in the message size, configured using CONFIG_LWM2M_COAP_MAX_MSG_SIZE. Special care should be taken to ensure that used CoAP block size CONFIG_LWM2M_COAP_BLOCK_SIZE can fit given message size with headers. Previous headroom was 48 bytes.

• TLS credential type TLS_CREDENTIAL_SERVER_CERTIFICATE was renamed and deprecated, use TLS_CREDENTIAL_PUBLIC_CERTIFICATE instead.

• arduino_uno_r4_minima and arduino_uno_r4_wifi board targets have been deprecated in favor of a new arduino_uno_r4 board with revisions (arduino_uno_r4@minima and arduino_uno_r4@wifi).

• esp32c6_devkitc board target has been deprecated and renamed to esp32c6_devkitc/esp32c6/hpcore.

• xiao_esp32c6 board target has been deprecated and renamed to xiao_esp32c6/esp32c6/hpcore.

• CONFIG_HAWKBIT_DDI_NO_SECURITY Kconfig option has been deprecated, because support for anonymous authentication had been removed from the hawkBit server in version 0.8.0.

• The CONFIG_BT_CONN_TX_MAX Kconfig option has been deprecated. The number of pending TX buffers is now aligned with the CONFIG_BT_BUF_ACL_TX_COUNT Kconfig option.

• The CONFIG_CRYPTO_TINYCRYPT_SHIM Kconfig option has been removed. It was deprecated since Zephyr 4.0, and users were advised to migrate to alternative crypto backends.

New APIs and options

• Architectures

  • NIOS2 Architecture was removed from Zephyr.

  • ARCH_HAS_VECTOR_TABLE_RELOCATION

  • CONFIG_SRAM_VECTOR_TABLE moved from zephyr/Kconfig.zephyr to zephyr/arch/Kconfig and added dependencies to it.

• Kernel

• K_TIMEOUT_ABS_SEC

• I2C

  • i2c_configure_dt().

• Bluetooth

  • Audio

    • BT_BAP_ADV_PARAM_CONN_QUICK

    • BT_BAP_ADV_PARAM_CONN_REDUCED

    • BT_BAP_CONN_PARAM_SHORT_7_5

    • BT_BAP_CONN_PARAM_SHORT_10

    • BT_BAP_CONN_PARAM_RELAXED

    • BT_BAP_ADV_PARAM_BROADCAST_FAST

    • BT_BAP_ADV_PARAM_BROADCAST_SLOW

    • BT_BAP_PER_ADV_PARAM_BROADCAST_FAST

    • BT_BAP_PER_ADV_PARAM_BROADCAST_SLOW

    • bt_csip_set_member_set_size_and_rank()

    • bt_csip_set_member_get_info()

  • Host

    • bt_le_get_local_features()

    • bt_le_bond_exists()

    • bt_br_bond_exists()

    • bt_conn_lookup_addr_br()

    • bt_conn_get_dst_br()

    • LE Connection Subrating is no longer experimental.

    • Remove deletion of the classic bonding information from bt_unpair(), and add bt_br_unpair().

    • Remove query of the classic bonding information from bt_foreach_bond(), and add bt_br_foreach_bond().

• Display

  • display_clear()

• Networking:

  • IPv4

    • CONFIG_NET_IPV4_MTU

  • MQTT

    • CONFIG_MQTT_VERSION_5_0

  • Sockets

    • CONFIG_NET_SOCKETS_INET_RAW

  • OpenThread

    • Moved OpenThread-related Kconfig options from subsys/net/l2/openthread/Kconfig to modules/openthread/Kconfig.

    • Refactored OpenThread networking API, see the OpenThread section of the migration guide.

    • CONFIG_OPENTHREAD_SYS_INIT

    • CONFIG_OPENTHREAD_SYS_INIT_PRIORITY

  • zperf

    • CONFIG_ZPERF_SESSION_PER_THREAD

    • zperf_upload_params.data_loader

• Sensor

  • sensor_value_to_deci()

  • sensor_value_to_centi()

• Stepper

  • stepper_stop()

• Storage

  • flash_area_copy()

• Counter

  • counter_reset()

• Sys

  • util_eq()

  • util_memeq()

• LoRaWAN

  • lorawan_request_link_check()

• Video

  • video_api_ctrl_t()

  • video_query_ctrl()

  • video_print_ctrl()

• PCIe

  • CONFIG_NVME_PRP_PAGE_SIZE

• Debug

  • Core Dump

    • CONFIG_DEBUG_COREDUMP_THREAD_STACK_TOP, enabled by default for ARM Cortex M when CONFIG_DEBUG_COREDUMP_MEMORY_DUMP_MIN is selected.

    • CONFIG_DEBUG_COREDUMP_BACKEND_IN_MEMORY

    • CONFIG_DEBUG_COREDUMP_BACKEND_IN_MEMORY_SIZE

• Other

  • CONFIG_LV_Z_COLOR_MONO_HW_INVERSION

• ZBus

  • Zbus has achieved stable status with the release of API version v1.0.0.

  • Runtime observers can work without heap. Now it is possible to choose between static, dynamic, and none allocation for the runtime observers nodes.

  • Runtime observers using CONFIG_ZBUS_RUNTIME_OBSERVERS_NODE_ALLOC_NONE must use the new function zbus_chan_add_obs_with_node().

  • CONFIG_ZBUS_RUNTIME_OBSERVERS_NODE_ALLOC_DYNAMIC

  • CONFIG_ZBUS_RUNTIME_OBSERVERS_NODE_ALLOC_STATIC

  • CONFIG_ZBUS_RUNTIME_OBSERVERS_NODE_ALLOC_NONE

  • CONFIG_ZBUS_RUNTIME_OBSERVERS_NODE_POOL_SIZE

New Boards

• Adafruit Industries, LLC

  • Adafruit Feather ESP32S2 (adafruit_feather_esp32s2)

  • Adafruit Feather ESP32S2 TFT (adafruit_feather_esp32s2_tft)

  • Adafruit Feather ESP32S2 TFT Reverse (adafruit_feather_esp32s2_tft_reverse)

  • Adafruit Feather ESP32S3 (adafruit_feather_esp32s3)

  • Adafruit Feather ESP32S3 TFT (adafruit_feather_esp32s3_tft)

• Advanced Micro Devices (AMD), Inc.

  • Versal NET RPU development board (versalnet_rpu)

• Aesc Silicon

  • ElemRV-N (elemrv)

• aithinker

  • Ai-Thinker WB2-12F development board (ai_wb2_12f)

• Ambiq Micro, Inc.

  • Apollo510 SOC Evaluation Board (apollo510_evb)

• Analog Devices, Inc.

  • max32657evkit (max32657evkit)

• BeagleBoard.org Foundation

  • PocketBeagle 2 (pocketbeagle_2)

• Blues Wireless

  • Cygnet (cygnet)

• Bouffalo Lab (Nanjing) Co., Ltd.

  • BL604E IOT DVK development board (bl604e_iot_dvk)

• Espressif Systems

  • ESP32-DevKitC (esp32_devkitc)

• Ezurio

  • BL54L15 DVK (bl54l15_dvk)

  • BL54L15u DVK (bl54l15u_dvk)

• FANKE Technology Co., Ltd.

  • FK743M5-XIH6 (fk743m5_xih6)

• IAR Systems AB

  • STM32F429II-ACA (stm32f429ii_aca)

• Intel Corporation

  • Bartlett Lake P CRB (intel_btl_s_crb)

• ITE Tech. Inc.

  • IT51XXX series (it515xx_evb)

• KWS Computersysteme Gmbh

  • Pico2-SPE (pico2_spe)

  • Pico-SPE (pico_spe)

• Lilygo Shenzhen Xinyuan Electronic Technology Co., Ltd

  • T-Dongle S3 (tdongle_s3)

  • TTGO TBeam (ttgo_tbeam)

  • TTGO T-OI-PLUS (ttgo_toiplus)

  • T-Watch S3 (twatch_s3)

• Microchip Technology Inc.

  • MEC17xxEVB ASSY6941 (mec_assy6941)

• Nuvoton Technology Corporation

  • NUMAKER M55M1 (numaker_m55m1)

• NXP Semiconductors

  • FRDM-MCXA153 (frdm_mcxa153)

  • FRDM-MCXA166 (frdm_mcxa166)

  • FRDM-MCXA276 (frdm_mcxa276)

  • MCX-N9XX-EVK (mcx_n9xx_evk)

• Octavo Systems LLC

  • OSD32MP1-BRK (osd32mp1_brk)

• OpenHW Group

  • cv32a6_genesys_2 (cv32a6_genesys_2)

  • cv64a6_genesys_2 (cv64a6_genesys_2)

• Pimoroni Ltd.

  • Pimoroni Pico Plus2 (pico_plus2)

• QEMU

  • QEMU Emulation for Renesas RX (qemu_rx)

• Renesas Electronics Corporation

  • Renesas Starter Kit for RX130 (rsk_rx130)

  • RZ/A2M Evaluation Kit (rza2m_evk)

  • RZ/A3UL SMARC Evaluation Board Kit (rza3ul_smarc)

  • RZ/G2L SMARC Evaluation Board Kit (rzg2l_smarc)

  • RZ/G2LC SMARC Evaluation Board Kit (rzg2lc_smarc)

  • Renesas Starter Kit+ for RZ/N2L (rzn2l_rsk)

  • Renesas Starter Kit+ for RZ/T2L (rzt2l_rsk)

  • Renesas Starter Kit+ for RZ/T2M (rzt2m_rsk)

  • RZ/V2L SMARC Evaluation Board Kit (rzv2l_smarc)

• Seeed Technology Co., Ltd

  • XIAO MG24 (xiao_mg24)

  • XIAO RA4M1 (xiao_ra4m1)

• sensry.io

  • Ganymed Starter Kit (SK) (ganymed_sk)

• Shanghai Ruiside Electronic Technology Co., Ltd.

  • ART-Pi2 (art_pi2)

• Silicon Laboratories

  • EFR32xG21 2.4 GHz 20 dBm (SLWRB4180B) (slwrb4180b)

• STMicroelectronics

  • Nucleo F439ZI (nucleo_f439zi)

  • Nucleo WBA65RI (nucleo_wba65ri)

  • STM32H757I Eval (stm32h757i_eval)

  • STM32MP135F-DK Discovery (stm32mp135f_dk)

  • STM32U5G9J Discovery Kit (stm32u5g9j_dk2)

• Texas Instruments

  • SK-AM64 (sk_am64)

• Variscite Ltd.

  • VAR-SOM-MX8M-PLUS (imx8mp_var_som)

• WinChipHead

  • WCH CH32V003F4P6 Development Board (ch32v003f4p6_dev_board)

  • WCH LinkW (linkw)

• WIZnet Co., Ltd.

  • W5500-EVB-Pico2 (w5500_evb_pico2)

• Würth Elektronik GmbH.

  • Ophelia-IV DK (ophelia4ev)

New Drivers

• ADC

  • adi,ad4050-adc

  • adi,ad4052-adc

  • adi,ad4130-adc

  • ite,it51xxx-adc

  • realtek,rts5912-adc

  • renesas,rz-adc

• Audio

  • ti,tlv320aic3110

• Charger

  • ti,bq25713

  • x-powers,axp2101-charger

• Clock control

  • ite,it51xxx-ecpm

  • nordic,nrfs-audiopll

  • renesas,rx-cgc-pclk

  • renesas,rx-cgc-pclk-block

  • renesas,rx-cgc-pll

  • renesas,rx-cgc-root-clock

  • renesas,rza2m-cpg

  • st,stm32mp13-cpu-clock-mux

  • st,stm32mp13-pll-clock

  • wch,ch32v20x_30x-pll-clock

• Comparator

  • renesas,ra-acmphs

  • renesas,ra-acmphs-global

• Counter

  • ite,it8xxx2-counter

  • neorv32,gptmr

  • realtek,rts5912-timer

  • wch,gptm

  • zephyr,native-sim-counter

• CPU

  • intel,bartlett-lake

  • openhwgroup,cva6

  • renesas,rx

  • wch,qingke-v4c

  • zephyr,native-sim-cpu

• Cryptographic accelerator

  • ti,cc23x0-aes

• DAC

  • ti,dac161s997

• Display

  • sinowealth,sh1122

  • sitronix,st75256

  • sitronix,st7567

  • sitronix,st7701

  • solomon,ssd1320

• DMA

  • renesas,rz-dma

  • ti,cc23x0-dma

  • wch,wch-dma

• Ethernet

  • st,stm32-ethernet-controller

  • st,stm32n6-ethernet

  • ti,dp83867

  • xlnx,axi-ethernet-1.00.a

• Firmware

  • nordic,ironside-call

  • nxp,scmi-cpu

• Flash controller

  • renesas,rx-flash

  • silabs,series2-flash-controller

• File system

  • zephyr,fstab,fatfs

• GPIO and Headers

  • adi,max14915-gpio

  • adi,max14917-gpio

  • adi,max22199-gpio

  • bflb,gpio

  • espressif,esp32-lpgpio

  • ite,it51xxx-gpio

  • nxp,lcd-pmod

  • raspberrypi,pico-gpio-port

  • renesas,ra-parallel-graphics-header

  • renesas,rx-gpio

  • renesas,rza2m-gpio

  • renesas,rza2m-gpio-int

• I2C

  • cdns,i2c

  • ite,it51xxx-i2c

  • litex,litei2c

  • renesas,ra-i2c-sci-b

  • renesas,rz-riic

  • sensry,sy1xx-i2c

  • wch,i2c

• I3C

  • ite,it51xxx-i3cm

  • ite,it51xxx-i3cs

• Input

  • ite,it51xxx-kbd

  • realtek,rts5912-kbd

  • st,stm32-tsc

  • tsc-keys

  • vishay,vs1838b

• Interrupt controller

  • ite,it51xxx-intc

  • ite,it51xxx-wuc

  • ite,it51xxx-wuc-map

  • renesas,rx-icu

• LED

  • dac-leds

  • x-powers,axp192-led

  • x-powers,axp2101-led

• Mailbox

  • arm,mhuv3

  • renesas,rz-mhu-mbox

• MDIO

  • xlnx,axi-ethernet-1.00.a-mdio

• Memory controller

  • adi,max32-hpb

  • realtek,rts5912-bbram

  • st,stm32-xspi-psram

• MFD

  • adi,maxq10xx

  • ambiq,iom

  • x-powers,axp2101

• MIPI DBI

  • nxp,mipi-dbi-dcnano-lcdif

• Miscellaneous

  • nordic,nrf-mpc

  • renesas,ra-ulpt

  • renesas,rx-sci

  • renesas,rz-sci

• Multi-bit SPI

  • snps,designware-ssi

• MTD

  • fixed-subpartitions

  • jedec,mspi-nor

  • renesas,ra-nv-code-flash

  • renesas,ra-nv-data-flash

  • renesas,rx-nv-flash

• Networking

  • nordic,nrf-nfct-v2

• Pin control

  • ambiq,apollo5-pinctrl

  • arm,mps2-pinctrl

  • arm,mps3-pinctrl

  • arm,v2m_beetle-pinctrl

  • bflb,pinctrl

  • renesas,rx-pinctrl

  • renesas,rx-pinmux

  • renesas,rza-pinctrl

  • renesas,rza2m-pinctrl

  • renesas,rzn-pinctrl

  • renesas,rzt-pinctrl

  • renesas,rzv-pinctrl

  • wch,20x_30x-afio

• Power management

  • realtek,rts5912-ulpm

• PWM

  • arduino-header-pwm

  • neorv32,pwm

  • realtek,rts5912-pwm

  • silabs,siwx91x-pwm

  • wch,gptm-pwm

• Regulator

  • x-powers,axp2101-regulator

• Reset controller

  • reset-mmio

• RNG

  • adi,maxq10xx-trng

  • zephyr,native-sim-rng

• RTC

  • nxp,pcf2123

  • realtek,rts5912-rtc

• SDHC

  • ambiq,sdio

  • xlnx,versal-8.9a

• Sensors

  • bosch,bmm350

  • everlight,als-pt19

  • invensense,icm45686

  • invensense,icp201xx

  • liteon,ltr329

  • meas,ms5837-02ba

  • meas,ms5837-30ba

  • pixart,paa3905

  • pixart,paj7620

  • pixart,pat9136

  • st,lsm6dsv32x

  • vishay,veml6031

  • we,wsen-itds-2533020201601

• Serial controller

  • bflb,uart

  • espressif,esp32-lpuart

  • ite,it51xxx-uart

  • renesas,rx-uart-sci

  • renesas,rx-uart-sci-qemu

  • renesas,rz-sci-uart

  • renesas,rza2m-scif-uart

  • zephyr,native-pty-uart

• SPI

  • cdns,spi

  • silabs,gspi

  • ti,cc23x0-spi

• Stepper

  • adi,tmc51xx

• Tachometer

  • ite,it51xxx-tach

  • realtek,rts5912-tach

• Timer

  • ite,it51xxx-timer

  • renesas,ra-ulpt-timer

  • renesas,rx-timer-cmt

  • renesas,rx-timer-cmt-start-control

  • renesas,rza2m-ostm

• USB

  • adi,max32-usbhs

  • st,stm32n6-otghs

• Watchdog

  • ite,it51xxx-watchdog

  • realtek,rts5912-watchdog

  • renesas,ra-wdt

  • silabs,siwx91x-wdt

  • wch,iwdg

New Samples

• BMG160 3-axis gyroscope

• Debug ULP

• Echo ULP

• Fatfs filesystem fstab

• Network packet filter

• PAJ7620 Gesture Sensor

• Barometric pressure and temperature sensor interrupt example

• Barometric pressure and temperature sensor polling example

• Renesas comparator

• OpenAMP Linux Zephyr RPMsg

• SPIS wake up

• Stepper

• UART ASYNC API

• UUID

• VEML6031 High Accuracy Ambient Light Sensor

Other notable changes

• Added support for Armv8.1-M MPU’s PXN (Privileged Execute Never) attribute. With this, the MPU attributes for __ramfunc and __ram_text_reloc were modified such that, PXN attribute is set for these regions if compiled with CONFIG_ARM_MPU_PXN and CONFIG_USERSPACE. This results in a change in behaviour for code being executed from these regions because, if these regions have pxn attribute set in them, they cannot be executed in privileged mode.

• Removed support for Nucleo WBA52CG board (nucleo_wba52cg) since it is NRND (Not Recommended for New Design) and it is not supported anymore in the STM32CubeWBA from version 1.1.0 (July 2023). The migration to Nucleo WBA55CG (nucleo_wba55cg) is recommended instead.

• Updated Mbed TLS to version 3.6.3 (from 3.6.2). The release notes can be found at: https://github.com/Mbed-TLS/mbedtls/releases/tag/mbedtls-3.6.3

• Updated TF-M to version 2.1.2 (from 2.1.1). The release notes can be found at: https://trustedfirmware-m.readthedocs.io/en/tf-mv2.1.2/releases/2.1.2.html