VulnerabilityPublished 13 Nov 2026

CVE-2026-127915: mcu-tools mcuboot · Bounds

Affects mcu-tools mcubootSource CVE Database V5

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Not known to be exploited · CVSS 2.0 Low : upgrade to 2.5.0 when convenient.

Data as of 13 Nov 2026, 01:45 UTC

CVSS 3.1 base score

2.0Low

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	2.0

Patch: Available – fixed in 2.5.0

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

Attack Vector: Physical
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: Physical: The attack requires the attacker to physically touch or manipulate the vulnerable component. Physical interaction may be brief or persistent.
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 >=0.9.0 <2.5.0	Fixed in 2.5.0
GitHubmcuboot`pkg:github/mcuboot`Other threats	Affected >=0.9.0 <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 validates each TLV entry's header and payload against the TLV area boundary inside the iterator. Users should upgrade to version 2.5.0 or later to remediate this issue. No additional mitigation is required for default flash builds as the impact is contained by existing runtime checks.

Description

CVE-2026-127915 is a low-severity vulnerability in the MCUboot bootloader's TLV iterator function bootutil_tlv_iter_next(). It improperly validates bounds when parsing image trailer TLVs, allowing a crafted image to cause a bounded out-of-region read during pre-authentication. The impact is limited by multiple runtime checks and memory bounds enforcement in typical configurations, resulting in a validation failure rather than memory corruption or data disclosure. The vulnerability is fixed in MCUboot version 2.5.0.

Impact

The vulnerability allows a crafted image to cause a bounded out-of-region read during TLV parsing before signature verification. In default configurations, this read is confined to the attacker's own flash partition and is not observable, resulting in a validation failure without memory corruption or information disclosure. Under the non-default MCUBOOT_RAM_LOAD configuration, the unchecked memcpy can lead to a genuine out-of-bounds read, potentially causing memory safety issues. There is no known exploitation in the wild.

Summary

The MCUboot TLV iterator function bootutil_tlv_iter_next() in bootutil/src/tlv.c uses a single loop guard and advances by a length field controlled by the attacker without validating that the TLV header and payload remain within the declared TLV area. This can cause a 4-byte header read up to 3 bytes past the TLV boundary and a payload description that extends beyond the TLV area. Since TLVs are parsed before signature verification, a crafted image can trigger this during boot. However, multiple guards limit the impact: the TLV area size is capped by bootutil_max_image_size(), flash_area_read() bounds-checks reads against the flash partition, and payload consumers clamp lengths before copying. In default flash builds, this results in a bounded out-of-region read confined to the attacker's partition with no observable effect. Under the non-default MCUBOOT_RAM_LOAD configuration, unchecked memcpy can cause a genuine out-of-bounds read. The fix is to validate each TLV entry's header and payload against the TLV area boundary inside the iterator. The vulnerability affects MCUboot versions >=0.9.0 and <2.5.0 and is fixed in 2.5.0.

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Exploitation evidence

What to do

Affected software

Description

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

Technical details

References

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