CVE-2026-128091

What it is

When MCUboot is built with the TinyCrypt crypto backend (MCUBOOT_USE_TINYCRYPT), bootutil_aes_ctr_drop() in boot/bootutil/include/bootutil/crypto/aes_ctr_tinycrypt.h was an empty stub. The AES-CTR context for this backend is the fully expanded AES-128 key schedule (struct tc_aes_key_sched_struct). Generic code relies on this hook to release and clear key state, so with TinyCrypt nothing was cleared. The mbedTLS and PSA backends do free or destroy their key state here. As a result, boot_state_clear(), which boot_go() calls before handing off to the application, left the image's AES content-encryption key schedule in the static boot_data state. This is the case after an encrypted upgrade in single-image builds, where boot_enc_zeroize() is not called. boot_decrypt_key() likewise left the ECIES-derived key-encryption key schedule on the stack. The affected build uses MCUBOOT_ENC_IMAGES with TinyCrypt, which is the default ECDSA and Ed25519 backend in the Zephyr port. The first AES-128 round key equals the cipher key, so anyone who can read the leftover bootloader RAM after boot can recover the image content key and decrypt that encrypted image. That includes a physical attacker with debug or RAM access, or code later running on the device. This weakens image-encryption key confidentiality (and so the confidentiality of the encrypted image's plaintext). The device's long-term private decryption key is not exposed, and image authenticity is not affected. The fix wipes the context with bootutil_wipe_memory().

At a glance

Exploitability

Can be exploited with physical access without logging in. Limited direct impact.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-11-13 02:18 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-11-13 02:18 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: not scored yet.
• Severity: 2.0 LOW (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-11-13 02:18 UTC

Last modified

2026-11-13 02:18 UTC

Weakness

CWE-226

Record status

Received

Attack profile CVSS 3.1 · 2.0

Attack vector

Physical

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-128091.md and follow it. Check whether this project is affected by CVE-2026-128091. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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