CVE-2026-75084 in Zephyr
Summary
by MITRE • 10/15/2026
The CC1200 sub-GHz IEEE 802.15.4 driver takes the PHY packet length from the first byte of the radio's RX FIFO in get_packet_length() and validates it in verify_rxfifo_validity() (drivers/ieee802154/ieee802154_cc1200.c). That validation only enforced a lower bound (pkt_len < 3); its second clause rejects a FIFO that holds more bytes than declared and therefore never bounds large values. Because the driver configures the radio for variable packet length with PKT_LEN = 0xFF, the length byte is an over-the-air value of 0-255 that reached net_pkt_rx_alloc_with_buffer() and the subsequent SPI burst read unclamped.
An unauthenticated attacker within radio range can transmit a frame that presents a length byte above the IEEE 802.15.4 maximum of 127 while the chip's 128-byte RX FIFO has not overflowed, so the driver's RX_FIFO_ERROR pre-check does not fire. Reaching this state depends on RF framing and timing, since the RX thread is driven off the PKT_SYNC_RXTX signal and may sample the FIFO before a packet is complete; no pairing, authentication, or user interaction is required.
With the default CONFIG_NET_BUF_FIXED_DATA_SIZE and CONFIG_NET_BUF_DATA_SIZE=128, an allocation larger than one fragment is satisfied by a chain of fragments, but read_rxfifo_content() performs a single SPI burst of pkt_len bytes into the first fragment's buf->data and then calls net_buf_add() with the same length. A length above 128 therefore writes up to 127 bytes past the end of a fragment in the contiguous rx_bufs pool and leaves a net_buf whose len exceeds its capacity. The overflowing bytes are FIFO-underflow output rather than attacker-chosen data, so the practical impact is network-buffer-pool corruption and crashes rather than a controlled write. Only builds that enable CONFIG_IEEE802154_CC1200 with an attached CC1200 radio are affected.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability in question resides within the IEEE 802.15.4 driver for the Texas Instruments CC1200 sub-GHz transceiver, specifically affecting systems where CONFIG_IEEE802154_CC1200 is enabled and a physical CC1200 radio module is attached to the host system. This flaw represents a critical failure in input validation during the reception of wireless frames, leading to memory corruption within the network buffer pool. The core technical issue stems from an incomplete bounds check implemented in the verify_rxfifo_validity function, which is invoked by get_packet_length when processing incoming packets. While the driver correctly enforces a lower bound on packet length to reject empty or malformed frames with fewer than three bytes, it fails to enforce an upper bound relative to the actual available data in the radio's receive FIFO buffer. This oversight allows the system to proceed with allocating network buffers based solely on the length byte extracted from the first position of the RX FIFO, without verifying that this declared length does not exceed the physical capacity of the hardware buffer or the allocated software structures.
The operational mechanics of this vulnerability are tied closely to the radio's configuration and the timing of data sampling. The CC1200 is configured for variable packet length with PKT_LEN set to 0xFF, meaning it accepts any length byte from zero to two hundred fifty-five transmitted over the air. When a frame arrives, the RX thread samples the FIFO content driven by the PKT_SYNC_RXTX signal. Due to RF framing and timing variations, there is a window where the driver may sample the initial bytes of a packet before the entire payload has been fully transferred into the hardware buffer or before the end-of-packet indicator is asserted. Consequently, an attacker within radio range can craft a malicious frame that declares a length byte exceeding one hundred twenty-seven, which is already above the maximum valid IEEE 802.15.4 MAC payload size of one hundred twenty-seven bytes. Because the hardware FIFO has not yet overflowed and the pre-check for RX_FIFO_ERROR does not trigger under these specific timing conditions, the driver accepts this invalid length value as legitimate data to be processed further into the network stack.
The impact on system stability is severe due to how memory allocation and buffer management are handled in the Zephyr networking subsystem with default configurations such as CONFIG_NET_BUF_FIXED_DATA_SIZE and CONFIG_NET_BUF_DATA_SIZE set to one hundred twenty-eight bytes. When a packet length exceeding this threshold is received, the net_pkt_rx_alloc_with_buffer function attempts to allocate network buffers. While larger allocations might be satisfied by chaining multiple fragments, the subsequent read_rxfifo_content routine performs a single SPI burst transfer of pkt_len bytes directly into the data buffer of the first fragment in that chain. Since the underlying contiguous rx_bufs pool and individual fragment structures are sized for one hundred twenty-eight bytes maximum, writing more than this amount results in an out-of-bounds write operation. The driver calls net_buf_add with the unclamped length value, causing the network buffer's internal length field to exceed its allocated capacity. This state corruption leads directly to memory pool degradation and system crashes rather than providing the attacker with a controlled arbitrary write primitive, as the overflowed bytes are derived from FIFO underflow output data rather than carefully crafted malicious payloads.
From a classification perspective, this vulnerability aligns with CWE-130 Improper Handling of Length Parameter Inconsistency and CWE-787 Out-of-bounds Write. The failure to validate that the declared packet length matches the actual available buffer space constitutes a classic logic error in input validation. Furthermore, because an unauthenticated attacker can trigger this condition remotely via wireless transmission without requiring any user interaction or authentication, it falls under MITRE ATT&CK technique T1059 Command and Scripting Interpreter if viewed through the lens of system compromise potential, though more accurately it represents a Denial of Service vector due to the resulting crash. The lack of pairing requirements makes this particularly dangerous in unsecured wireless environments where any device within range can exploit the flaw by simply transmitting oversized frames that trigger the buffer overflow path during normal reception processing.
Mitigation strategies must focus on enforcing strict upper bounds on packet lengths at multiple layers of the stack. First, the verify_rxfifo_validity function should be updated to check that the declared length does not exceed both the maximum IEEE 802.15.4 frame size and the physical capacity of the RX FIFO buffer before proceeding with allocation. Second, defensive programming practices dictate that any value read from hardware registers or external sources must be clamped against known safe limits prior to being used for memory operations such as SPI bursts or buffer allocations. In addition to code fixes, system administrators should ensure that firmware updates are applied if vendors release patches addressing this specific driver logic error. For environments where immediate patching is not possible, restricting the operational range of CC1200 devices through physical shielding or reducing transmit power can limit the attack surface by keeping potential attackers outside effective radio range until a permanent software fix is deployed.