VulnerabilityPublished 13 Nov 2026

CVE-2026-127916: mcu-tools mcuboot · Bounds

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 >=1.6.0 <2.5.0	Fixed in 2.5.0
GitHubmcuboot`pkg:github/mcuboot`Other threats	Affected >=1.6.0 <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 that adds safe addition of image size fields and bounds checks to ensure the image span fits within the flash area before hashing. Users should upgrade to version 2.5.0 or later to remediate this issue. No other mitigation is required as the vulnerability is addressed by this official fix.

Description

CVE-2026-127916 is a vulnerability in mcuboot's bootutil_img_hash() function where image size fields are summed and used to read flash memory without proper bounds checking. This can cause out-of-bounds reads up to 64 KB past the image slot or more on certain code paths, potentially causing read faults during image validation. The flaw exists because the image is hashed before signature verification, allowing an attacker who can place an image in a slot to trigger the issue. The vulnerability is fixed in mcuboot version 2.5.0 by adding safe addition and bounds checks before hashing.

Impact

The vulnerability can cause mcuboot to read beyond the allocated flash area during image validation, potentially triggering read faults that prevent the device from booting. No data disclosure occurs since the out-of-bounds bytes are only fed into the hash digest calculation, which is internal. The fault can recur on every boot if the image validation is repeated, causing persistent boot failures. The severity is low given the local attack vector (requires ability to place an image in a slot) and the impact limited to denial of service via boot failure.

Summary

The vulnerability in mcuboot's bootutil_img_hash() arises from the unchecked summation of image header size fields (ih_hdr_size, ih_img_size, ih_protect_tlv_size) to compute the image digest span. This span is read from flash without verifying it fits within the flash area, leading to potential out-of-bounds reads. Some code paths perform partial or no header validation before hashing, increasing exposure. The impact depends on the flash backend's handling of out-of-bounds reads: some return errors preventing over-read, while others (e.g., Cypress PSoC6 port) do not bound reads, causing faults. The vulnerability does not disclose data but can cause repeated read faults preventing device boot. The fix in version 2.5.0 uses safe addition and rejects images whose computed span exceeds flash area bounds before hashing.

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Exploitation evidence

What to do

Affected software

Description

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

Technical details

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