CVE-2026-14296 Overview
CVE-2026-14296 is a signature verification flaw [CWE-347] in MCUboot when configured with the Direct XIP update strategy on multi-core platforms. The main application image starts secondary cores, such as a radio core, using the currently active slot without additional verification. MCUboot in the bare upstream configuration assumes the system is bootable if at least one slot per image is available. This allows a mismatch where the main application boots from slot (a) but instructs the radio core to execute an unauthenticated image at the same address, bypassing image authenticity guarantees on the secondary core.
Critical Impact
An attacker on an adjacent network can cause a secondary core to execute an unverified firmware image, undermining secure boot on multi-image devices.
Affected Products
- MCUboot bootloader in bare (upstream) configuration using the Direct XIP update strategy
- Multi-image platforms with a main application core and secondary cores (for example, radio core)
- Nordic Semiconductor devices referenced in the vendor documentation
Discovery Timeline
- 2026-09-07 - CVE-2026-14296 published to the National Vulnerability Database (NVD)
- 2026-09-09 - Last updated in NVD database
Technical Details for CVE-2026-14296
Vulnerability Analysis
MCUboot supports multiple update strategies, including Direct eXecute-In-Place (XIP), which allows images to run directly from their primary or secondary slot without a copy step. On multi-image devices, MCUboot validates each image independently and marks it bootable if at least one valid slot exists. The main application, once launched, is responsible for starting other cores such as the radio core. It does so by passing the address of the currently active slot for the secondary image to that core.
The defect lies in the assumption that both images consistently boot from matching slot positions. When MCUboot selects slot (a) for the main application and slot (b) for the radio image, the main application still hands the secondary core the slot (a) address for the radio image. That address may hold an outdated, invalid, or attacker-supplied payload that was never authenticated by MCUboot for execution on the radio core.
Root Cause
The root cause is missing signature verification at the boundary between MCUboot and the runtime code that starts secondary cores [CWE-347]. MCUboot verifies each slot in isolation but does not enforce that the slot chosen for the secondary image matches the address used at runtime to start that core.
Attack Vector
Exploitation requires adjacent network access and high attack complexity. An attacker must place a crafted image in the alternate slot of the secondary image, such as the radio core, while ensuring the main application slot selection differs. On next boot, the main application will start the secondary core from an unauthenticated slot, resulting in execution of attacker-controlled firmware on that core with full confidentiality, integrity, and availability impact.
No public proof-of-concept exploit is available. Refer to the Nordic Semiconductor Documentation for platform-specific details on secure boot and slot management.
Detection Methods for CVE-2026-14296
Indicators of Compromise
- Unexpected firmware version or build identifier reported by a secondary core (for example, radio core) that does not match the deployed main application build.
- Boot logs showing MCUboot selecting different active slots for the main application and radio images across reboots.
- Presence of unsigned or previously superseded images in a secondary image slot that remain marked as bootable.
Detection Strategies
- Audit MCUboot configuration for use of the Direct XIP strategy combined with multi-image, multi-core deployments.
- Compare the running image hash on each core against the expected hash provisioned during the last authorized firmware update.
- Instrument the main application to log the slot address it passes to secondary cores and alert on mismatches with the active main-application slot.
Monitoring Recommendations
- Forward MCUboot and application boot telemetry to a centralized log store for cross-device correlation.
- Track firmware update transactions end-to-end so partial or failed updates that leave slots in inconsistent states are flagged.
- Monitor over-the-air update infrastructure for anomalous writes that target only one image slot in a multi-image bundle.
How to Mitigate CVE-2026-14296
Immediate Actions Required
- Inventory devices using MCUboot with Direct XIP and multi-image configurations, prioritizing those with independent update paths per core.
- Restrict physical and adjacent-network access to affected devices until a fix is deployed.
- Enforce atomic firmware updates that write and confirm both main application and radio images together, preventing mixed-slot boot states.
Patch Information
No patch identifier is included in the NVD entry for CVE-2026-14296. Consult the Nordic Semiconductor Documentation and upstream MCUboot project releases for updated Direct XIP handling and any vendor-specific System Architecture guidance addressing multi-image slot selection.
Workarounds
- Switch from Direct XIP to a swap-based MCUboot update strategy where feasible, so both images always execute from the primary slot after validation.
- Modify the main application to re-verify the signature of the secondary image at the address it is about to hand to the other core.
- Provision matching slot policies so that the main application and radio image are always updated and activated in the same slot position.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.