AES image key left on the stack after serial-recovery encrypted-image handling in MCUboot (CVE-2026-127928)
Published Last modified Sources: CVE.org, EUVD
What is affected, what to do
In MCUboot's serial-recovery encrypted-image support (boot/boot_serial/src/boot_serial_encryption.c), decrypt_image_inplace() and boot_image_validate_encrypted() each keep a stack-local struct boot_status. boot_enc_load() writes the plaintext per-image AES key into its enckey[] field. Neither function cleared this structure before returning.
Update Mcu-tools Mcuboot to version 2.5.0.
- Affected
- Mcu-tools Mcuboot
lt 1.9.0..2.5.0
- Mcu-tools Mcuboot
- Fixed in
- Mcu-tools Mcuboot
2.5.0
- Mcu-tools Mcuboot
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Metrics
2.0
XIEM Effective CVSS
Highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
2.0
CVSS v3
Severity Low on the scale from 0 to 10.
Source: CVE.org, EUVD
—
EPSS score
No value is available for this vulnerability.
Show all metrics
- Severity
- Low
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 40.00 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 2.0 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 2.0
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-226
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
In MCUboot's serial-recovery encrypted-image support (boot/boot_serial/src/boot_serial_encryption.c), decrypt_image_inplace() and boot_image_validate_encrypted() each keep a stack-local struct boot_status. boot_enc_load() writes the plaintext per-image AES key into its enckey[] field. Neither function cleared this structure before returning. In addition, a decrypt failure inside the per-sector loop of decrypt_image_inplace() returned early and skipped the total_out: cleanup, which left the expanded AES key context (enc_data) on the stack as well. The error paths of boot_image_validate_encrypted() similarly skipped boot_enc_zeroize(). The affected code is built when encrypted images (MCUBOOT_ENC_IMAGES, Zephyr CONFIG_BOOT_ENCRYPT_IMAGE) are combined with serial recovery. It runs when an encrypted image is uploaded to the primary slot over the recovery protocol, and when the image list or state is queried while an encrypted image is in the secondary slot. After these functions return, the image's AES content key remains in dead stack memory. An attacker who can later read device RAM, for example through a debug port or retained RAM, can recover it. This weakens the confidentiality of image-encryption keys within the bootloader trust boundary. A recovered key exposes the plaintext of the encrypted firmware image it protects. The device's long-term private decryption key is not exposed. No remote or recovery-protocol channel that returns this memory is known, so exploitation requires a separate memory-read capability.
Source: NVD (NIST), cvelistv5, CVE.org (MITRE), ENISA EUVD
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| mcu-tools | mcuboot |
|
|
Vendors and products
Weakness classes (CWE)
CWE-226Sensitive Information in Resource Not Removed Before Reuse
Base
The product releases a resource such as memory or a file so that it can be made available for reuse, but it does not clear or "zeroize" the information contained in the resource before the product performs a critical state transition or makes the resource available for reuse by other entities.
Entry at MITRE CWE-226
References & sources
- github.comFix commiteuvd, Patch
- github.comGHSA-hqmg-jwp9-8cf8euvd
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Receivedzephyrproject.org
CVSS V3.1: AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness type: CWE-226
Description added or changed
Show 6 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —In MCUboot's serial-recovery encrypted-image support (boot/boot_serial/src/boot_serial_encryption.c), decrypt_image_inplace() and boot_image_validate_encrypted() each keep a stack-local struct boot_status. boot_enc_load() writes the plaintext per-image AES key into its enckey[] field. Neither function cleared this structure before returning. In addition, a decrypt failure inside the per-sector loop of decrypt_image_inplace() returned early and skipped the total_out: cleanup, which left the expanded AES key context (enc_data) on the stack as well. The error paths of boot_image_validate_encrypted() similarly skipped boot_enc_zeroize(). The affected code is built when encrypted images (MCUBOOT_ENC_IMAGES, Zephyr CONFIG_BOOT_ENCRYPT_IMAGE) are combined with serial recovery. It runs when an encrypted image is uploaded to the primary slot over the recovery protocol, and when the image list or state is queried while an encrypted image is in the secondary slot. After these functions return, the image's AES content key remains in dead stack memory. An attacker who can later read device RAM, for example through a debug port or retained RAM, can recover it. This weakens the confidentiality of image-encryption keys within the bootloader trust boundary. A recovered key exposes the plaintext of the encrypted firmware image it protects. The device's long-term private decryption key is not exposed. No remote or recovery-protocol channel that returns this memory is known, so exploitation requires a separate memory-read capability.CVSS added —AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:NWeakness type (CWE) added —CWE-226Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/127xxx/CVE-2026-127928.json">CVE-2026-127928</a>Reference added —https://github.com/mcu-tools/mcuboot/commit/411949f830724617fbc08b9b32f0a45ba0c80bafReference added —https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-hqmg-jwp9-8cf8Source identifier: vulnerabilities@zephyrproject.org
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-127928"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-127928.svg?lang=en" alt="CVE-2026-127928 – NEOSEC Intel" height="20"></a>