VulnerabilityPublished 13 Nov 2026

CVE-2026-16671: mcu-tools mcuboot · Memory-safety

Affects mcu-tools mcubootSource CVE Database V5

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Not known to be exploited · CVSS 2.9 Low : upgrade to 2.5.0 when convenient.

Data as of 13 Nov 2026, 01:45 UTC

CVSS 3.1 base score

2.9Low

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (zephyr)	CVSS 3.1	2.9

Patch: Available – fixed in 2.5.0

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Local
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade mcu-tools mcuboot to 2.5.0.

Affected software

Product	Affected	Fixed in
mcu-toolsmcuboot	Affected >=2.0.0 <2.5.0	Fixed in 2.5.0
GitHubmcuboot`pkg:github/mcuboot`Other threats	Affected >=2.0.0 <2.5.0	Fixed in 2.5.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in mcuboot version 2.5.0. Users should upgrade to version 2.5.0 or later to resolve this vulnerability. No other mitigation is required as the overflow only occurs in non-default configurations and the impact is limited to boot instability.

Description

CVE-2026-16671 is a memory safety vulnerability in the mcuboot bootloader component of mcu-tools. It involves a fixed-size buffer overflow in the split_image_check() function when configured with certain non-default cryptographic digest algorithms larger than 32 bytes. This overflow can corrupt the bootloader's stack, potentially causing instability or boot failure. The vulnerability does not allow attacker-controlled code execution due to the fixed and non-attacker-controlled overflow content. A fix is available in mcuboot version 2.5.0.

Impact

The impact is limited to denial of service conditions such as bootloader instability or failed boot on affected configurations. There is no confidentiality, integrity, or privilege escalation impact, and no reliable code execution is possible due to the fixed and non-attacker-controlled overflow data. The CVSS score is low (2.9) reflecting the limited impact and high attack complexity.

Summary

The vulnerability arises because split_image_check() declares a fixed 32-byte buffer loader_hash to hold a SHA-256 digest, but passes it to bootutil_img_validate(), which copies IMAGE_HASH_SIZE bytes into it. IMAGE_HASH_SIZE is 64 for MCUBOOT_SHA512 or 48 for MCUBOOT_SIGN_EC384/SHA-384, causing an overflow of 16 or 32 bytes beyond the buffer. This overflow occurs only in non-default configurations requiring the legacy Mynewt split-image feature and larger digest sizes. The overflow overwrites the one-way digest of the loader image on the stack, leading to uncontrolled stack corruption that manifests as instability or boot failure rather than reliable code execution. The issue is fixed by resizing loader_hash to IMAGE_HASH_SIZE and passing the correct length. The vulnerability affects mcuboot versions >=2.0.0 and <2.5.0 and is resolved in version 2.5.0.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 00:52 UTC

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