AES-CTR Key Exposure in MCUboot with TinyCrypt Crypto Backend

CVE-2026-128091

What is CVE-2026-128091?

A vulnerability has been identified in MCUboot when using the TinyCrypt crypto backend, where the AES-CTR context is not properly cleared during the boot process. The function bootutil_aes_ctr_drop(), which is expected to manage key states, does not execute any operations in this backend. Consequently, potentially sensitive encryption keys remain in memory, making them accessible to anyone with the ability to read the bootloader RAM post-boot. This situation poses a risk, particularly in environments where physical access to devices is achievable. Although the long-term decryption key remains secure, the compromised image encryption key could allow unauthorized decryption of sensitive content. A fix is implemented to ensure that memory is wiped appropriately to mitigate this risk.

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