CVSS 3.1
2.0 lowCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:NCVE-2026-127928 AES image key left on the stack after serial-recovery encrypted-image handling in MCUboot
Low (2.0) in mcu-tools mcuboot. EPSS 0.08% estimated probability of exploitation activity in the next 30 days.
On this page
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.
Severity
- EPSS
- 0.08% estimated probability of exploitation activity in the next 30 days; 0th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-226 Sensitive Information in Resource Not Removed Before Reuse
- Published
- Modified
- Assigned by
- zephyr (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
Ask an AI about this CVE
Show the prompt
Explain CVE-2026-127928 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-127928?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-127928?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-127928 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Badge for a README or a site
An image that stays current: it is drawn from the data each time it is fetched (a host that proxies images, as GitHub does, may show its copy for a while). Markdown:
[](https://cve.bz/cve/CVE-2026-127928)
HTML:
<a href="https://cve.bz/cve/CVE-2026-127928"><img src="https://cve.bz/cve/badge/CVE-2026-127928.svg" alt="CVE-2026-127928"></a>
Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| mcu-tools mcuboot | from 1.9.0 before 2.5.0 |
Attack patterns (CAPEC)
- CAPEC-37 Retrieve Embedded Sensitive Data Likelihood: High · Severity: Very High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.