# CVE-2026-75085: Out-of-bounds read from received-frame length underflow in the STM32WBA IEEE 802.15.4 driver

Status: published. Published: 2026-10-14. Updated: 2026-11-04.

The STM32WBA IEEE 802.15.4 driver in drivers/ieee802154/ieee802154_stm32wba.c computed the packet length of a received frame as pkt_len = rx_frame->length - IEEE802154_FCS_LENGTH without first checking that the radio-reported length could hold an FCS. pkt_len is a uint8_t, so a reported length of 0 or 1 wrapped to 254 or 255. The only bound on the resulting value was __ASSERT_NO_MSG(pkt_len <= CONFIG_NET_BUF_DATA_SIZE), which compiles to nothing in the default production configuration (CONFIG_ASSERT=n).

The length originates in the ST link-layer receive-done metadata (p_metadata->length, stored by stm32wba_802154_receive_done()), and ultimately in the PHY header of a frame received over the air, so it is influenced by any attacker within radio range of the device. Reaching the underflow requires the vendor link layer to surface a frame shorter than the FCS with no error; the driver performed no validation of its own on that value.

When the underflow occurs, stm32wba_802154_rx_thread() calls net_pkt_write(pkt, rx_frame->psdu, pkt_len) with a length of about 254 bytes against a receive buffer that holds at most one PHY packet (IEEE802154_MAX_PHY_PACKET_SIZE, 127 bytes). This reads roughly 128 bytes past the end of the radio receive buffer and copies that adjacent memory into a network packet that is submitted to the networking stack, giving an out-of-bounds read with a potential disclosure of adjacent RAM plus needless oversized packet allocation in the RX thread.

The fix rejects a frame whose reported length is smaller than IEEE802154_FCS_LENGTH before the subtraction, and replaces the compiled-out assertion with a runtime length check that drops oversized frames — matching the runtime check already present in drivers/ieee802154/ieee802154_nrf5.c.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/46f8af4f5ee472abc13b0291c44fdfe4ed879aaa

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 4.3.0; < 4.3.2 (affected, semver); ≥ 4.4.0; < 4.5.0 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 4.2 (medium); CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L; source: CNA: zephyr

- CVSS 3.1: 4.2 (medium); CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L; source: NVD: vulnerabilities@zephyrproject.org

- CISA KEV: No listing in collected sources

- EPSS: 0.21% as of 2026-11-03; percentile 10.59%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/46f8af4f5ee472abc13b0291c44fdfe4ed879aaa (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w7pm-4r95-c9vr (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/commit/46f8af4f5ee472abc13b0291c44fdfe4ed879aaa (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w7pm-4r95-c9vr (vulnerabilities@zephyrproject.org)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-75085; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-75085; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-75085; retrieved 2026-11-04; source updated Not reported

Revision: b15b3e5c58b2eb5ace87d0a8dda77a1ba410ea2a599da30e24bd61649e539ccc

Canonical: https://y2.dev/cve/CVE-2026-75085

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