CVE-2026-1679: 
NixOS vulnerability analysis and mitigation

CVE-2026-1679 is a classic buffer overflow (CWE-120) vulnerability in the Zephyr RTOS eswifi socket offload driver. The driver copies user-provided payloads into a fixed-size buffer (eswifi->buf) without validating the payload length, allowing oversized sends to corrupt kernel memory. All Zephyr versions up to and including 4.3.0 are affected. The vulnerability was published on March 27–28, 2026, and carries a CVSS v3.1 base score of 7.3–7.8 (High), depending on the scoring authority (Zephyr Advisory, Red Hat).

The root cause is in eswifi_socket_send() within drivers/wifi/eswifi/eswifi_socket_offload.c (lines 288–295). The function first writes a header into eswifi->buf using snprintk(eswifi->buf, sizeof(eswifi->buf), "S3=%u\r", len), then calculates offset = strlen(eswifi->buf) and performs memcpy(&eswifi->buf[offset], buf, len) with no bounds check against the remaining buffer space. The buffer size is bounded by CONFIG_WIFI_ESWIFI_MAX_DATA_SIZE. Any payload larger than sizeof(eswifi->buf) - header_length will write past the end of the buffer before eswifi_request is called. Exploitation requires local code execution with the ability to call the socket send API; no remote attack path exists (Zephyr Advisory).

Successful exploitation can corrupt kernel memory, leading to denial of service (system crash), data integrity violations, and potential privilege escalation or arbitrary code execution within the kernel context. The attack surface is limited to Zephyr applications that use the eswifi socket offload driver and can invoke the socket send path locally. Confidentiality impact is rated low to high depending on the scoring source, while integrity and availability impacts are both rated high (Zephyr Advisory, Red Hat).

A proof-of-concept (PoC) exploit is publicly available as a downloadable tarball (eswifi-socket-send-buffer-overflow-poc.tar.gz) hosted in the Zephyr security advisory. The PoC uses an ASAN harness and Makefile to demonstrate the buffer overflow crash in eswifi_socket_send without achieving full remote code execution. There is no evidence of in-the-wild exploitation at this time, and the vulnerability is not listed in the CISA KEV catalog. The EPSS score is approximately 0.035% (very low probability of exploitation in the near term) (Zephyr Advisory).

1. Identify target: Confirm the target Zephyr device uses the eswifi socket offload driver and runs Zephyr version ≤ 4.3.0. This driver is typically present in IoT/embedded devices using the ES-WiFi module.
2. Gain local code execution: Obtain the ability to execute code locally on the Zephyr device (e.g., via a malicious application, compromised firmware update, or physical access to a debug interface such as JTAG/UART).
3. Craft oversized payload: Prepare a socket send call with a payload buffer larger than CONFIG_WIFI_ESWIFI_MAX_DATA_SIZE minus the header size written by snprintk (e.g., "S3=%u\r").
4. Invoke socket send API: Call the socket send API targeting the eswifi offload driver with the oversized buffer. The driver will write the header, compute the offset, and then memcpy the full payload past the end of eswifi->buf.
5. Trigger kernel memory corruption: The out-of-bounds write corrupts adjacent kernel memory, potentially causing a crash (DoS) or, with careful payload crafting, enabling privilege escalation or code execution in the kernel context.
6. Validate with ASAN: Using the public PoC (cd eswifi-socket-send-buffer-overflow-poc && make clean && make run), ASAN will report the buffer overflow, confirming the vulnerable code path (Zephyr Advisory).

• Logs: Unexpected kernel panic or fault logs originating from the eswifi driver or WiFi subsystem; ASAN reports referencing eswifi_socket_send in development/test environments.
• Process/Runtime Behavior: Abnormal system resets or crashes on Zephyr devices using the eswifi driver, particularly following socket send operations; unexpected memory fault exceptions in the WiFi driver stack.
• File System: Presence of eswifi-socket-send-buffer-overflow-poc.tar.gz or related PoC artifacts on development systems connected to target devices.
• Network: Unusual or malformed WiFi socket send operations with payloads exceeding CONFIG_WIFI_ESWIFI_MAX_DATA_SIZE bytes directed at the eswifi interface (Zephyr Advisory).

The Zephyr security advisory references a patch in the main branch via pull request #102119; users should update to a Zephyr version that includes this fix (beyond 4.3.0). No patched release version was explicitly named at the time of advisory publication. As a workaround, restrict local access and user privileges on affected devices, and where possible, disable or avoid use of the eswifi socket offload driver until a patched build is available. Monitor for suspicious socket send operations with oversized payloads as an interim detection measure (Zephyr Advisory).

The vulnerability was discovered and reported by SecMate (https://secmate.dev), credited in the Zephyr security advisory. Red Hat has tracked the CVE in their security database. Social media activity includes posts on Bluesky referencing the CVE, and the advisory was covered by security aggregators such as VulDB and InfinitSec. Community reaction has been measured given the local-only attack vector and the niche nature of the eswifi driver (Zephyr Advisory, Red Hat).