# CVE-2026-19673: Zephyr RTOS ethernet_recv buffer length validation bypass

Source: https://junglewise.ai/threats/cve-2026-19673-ethernet-recv-in-subsys-net-l2-ethernet-ethernet-c-validates-only  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-14. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-19673 · Severity: high · CVSS 7.1 · Published 2026-10-14

Zephyr RTOS is a real-time operating system used in embedded IoT and industrial devices. A flaw in Ethernet frame processing allows an attacker to send a specially crafted network frame as small as 14 bytes that causes the system to crash, read sensitive memory, or corrupt data. Only devices with VLAN networking enabled are affected.

Technologies: [Zephyr Project Zephyr RTOS](https://junglewise.ai/threats/technologies/zephyr). Vendors: [Zephyr Project](https://junglewise.ai/threats/vendors/zephyr-project).

## Quick answers

**Is CVE-2026-19673 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19673 being exploited in the wild.

**How severe is CVE-2026-19673?** High severity, with a CVSS score of 7.1, published 14 October 2026.

**Which products and versions are affected?** Zephyr Project Zephyr RTOS Versions with CONFIG_NET_VLAN enabled and ETHERNET_HW_VLAN_TAG_STRIP disabled.

**Is there a fix for CVE-2026-19673?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-19673 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-19673?** Check whether you run Zephyr Project Zephyr RTOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in ethernet_recv() where VLAN-tagged frames (ethertype 0x8100) trigger reinterpretation of a 14-byte buffer as an 18-byte structure without re-validating length. This causes a uint16_t underflow in the buffer length to 65534, allowing out-of-bounds reads and writes. An unauthenticated attacker on the network can send a 14–17 byte broadcast frame with VLAN ethertype to trigger the flaw; no prior knowledge of VLAN configuration is needed.

## Affected products

- Zephyr Project Zephyr RTOS Versions with CONFIG_NET_VLAN enabled and ETHERNET_HW_VLAN_TAG_STRIP disabled

## Timeline

- 2026-10-14: disclosed

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