CVE-2026-16664

What it is

MCUboot's Zephyr serial-recovery upload handler bs_upload() in boot/boot_serial/src/boot_serial.c decodes the host-supplied image field of an MCUmgr image-upload request into img_num (a full 32-bit value) and latches it on the off == 0 packet without any range check. It then passes img_num straight to flash_area_id_from_multi_image_slot(img_num, 0), which on the Zephyr port resolves to __flash_area_ids_for_slot() in boot/zephyr/include/sysflash/sysflash.h and indexes the static const int all_slots[] table as all_slots[img_num 2]. That table holds only MCUBOOT_IMAGE_NUMBER 2 entries, so any img_num >= MCUBOOT_IMAGE_NUMBER is an out-of-bounds read. The path is reachable by anyone with access to the serial / SMP recovery console, which is unauthenticated by design, and the bad value is supplied before any image signature is verified. The defect is specific to the default non-direct upload path (MCUBOOT_SERIAL_DIRECT_IMAGE_UPLOAD disabled) on the Zephyr port with the array-backed slot layout (not CONFIG_SINGLE_APPLICATION_SLOT). It is not gated on a multi-image configuration: MCUBOOT_IMAGE_NUMBER defaults to 1, so even a default single-image build is affected for any image >= 1. The MCUBOOT_SERIAL_DIRECT_IMAGE_UPLOAD path is safe (its flash_area_id_from_direct_image() switch returns -EINVAL for unknown indices). flash_area_id_from_multi_image_slot() takes a signed int image_index while img_num is uint32_t, so the attacker controls the sign of the index as well as its magnitude: an image of 0xFFFFFFFF converts to -1 and reads all_slots[-2], off the front of the table, while large positive values read off the end (CWE-192). Either way the index multiply img * 2 is performed in int, so a wild offset yields a bus/hard fault, giving a reliable denial of service of the bootloader during recovery. For moderately out-of-range indices the read returns adjacent .rodata as a garbage flash-area id that is handed to flash_area_open(); this normally fails with MGMT_ERR_EINVAL, but if the garbage id happens to match a valid non-image partition, the subsequent erase/write can target a partition outside the image set (CWE-787). The attacker-supplied value is never echoed back, so there is no information disclosure. The fix is to reject img_num >= BOOT_IMAGE_NUMBER on the off == 0 packet, before the slot lookup. The comparison must be made on the unsigned img_num: an equivalent guard applied after the conversion to int would not reject the negative case above. __flash_area_ids_for_slot() should bounds-check its own arguments as defence in depth. This vulnerability was reported independently twice: by NVIDIA Project Vanessa on 2026-06-22, and by Kai Phan (@kaimandalic) on 2026-07-19 as GHSA-8v33-88p6-jffj, which is closed as a duplicate of this advisory. Both original reports are reproduced in full below.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. Limited direct impact.

Fix

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

Timeline

1. 2026-07-22 19:47 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-11-13 02:18 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 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: 5.1 MEDIUM (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-129

Record status

Received

Attack profile CVSS 3.1 · 5.1

Attack vector

Local

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

Low

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-2026-16664.md and follow it. Check whether this project is affected by CVE-2026-16664. 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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