The Espressif AES driver in Zephyr exposes a multi‑session API that should provide distinct keys per session. However, the driver programs the hardware key registers outside the session‑level mutex, so the registers are overwritten by any subsequent session. When a second session is opened with a different key, further operations on the first session silently use the second session’s key and mode. This race condition (CWE-362) can be induced by a protocol peer that creates a new session, allowing an attacker to control which key is resident during a victim’s operation. The result is a cryptographic failure: data the application believes is protected with one key may in fact be encrypted or decrypted with an attacker‑known key, exposing plaintext or inverting the operation. Because the flaw only affects key management, no memory corruption occurs, but confidentiality is compromised.

Zephyr Project’s Zephyr RTOS, specifically the Espressif ESP32 hardware crypto driver. The vulnerability arises when an application opens two or more concurrent AES sessions with distinct keys. No built‑in Zephyr subsystem currently uses multiple sessions, so the risk lies with third‑party application code.

The CVSS score of 3.7 indicates a low severity. The EPSS score is not available and the vulnerability is not listed in CISA’s KEV catalog. The likely attack vector is via a protocol that triggers session creation on the device, giving an attacker remote influence over the key state. While the flaw does not directly trigger memory corruption or obvious denial‑of‑service, the ability to switch keys can lead to data exposure or operation inversion. The risk is therefore low and contingent upon the application’s use of multi‑session AES calls.