TLV iterator does not bound each entry against the declared TLV area in MCUboot bootutil

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-127915
StatePUBLISHED
Assignerzephyr
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-13 02:18:55 UTC
Updated2026-11-13 02:18:55 UTC
DescriptionThe MCUboot TLV iterator bootutil_tlv_iter_next() in boot/bootutil/src/tlv.c walks image trailer TLVs with a single loop guard (it->tlv_off < it->tlv_end) and advances by sizeof(struct image_tlv) + tlv.it_len using the attacker-controlled it_len field, without validating that the entry's header or payload stays within it->tlv_end. As a result the 4-byte header read can extend up to 3 bytes past the declared TLV area, and the returned (off, len) can describe a payload that runs past it. The path is pre-authentication: TLVs are parsed during bootutil_img_validate() before the signature is verified, and a crafted image can be presented through DFU / serial-recovery / OTA. However the impact is contained by surrounding guards: bootutil_img_validate() first rejects a TLV area larger than bootutil_max_image_size(), the default LOAD_IMAGE_DATA sink is flash_area_read() which bounds-checks against the flash partition and fails an out-of-partition read, and every payload consumer (EXPECTED_HASH_TLV, EXPECTED_KEY_TLV, EXPECTED_SIG_TLV, IMAGE_TLV_SEC_CNT) clamps len against a fixed buffer before copying. The residual effect in a default flash build is therefore an out-of-region read confined to the attacker's own slot partition whose result is never observable, yielding at worst a clean validation failure rather than memory corruption or information disclosure. A genuine (though still bounded) out-of-bounds read remains under the non-default MCUBOOT_RAM_LOAD configuration, where LOAD_IMAGE_DATA is an unchecked memcpy. The fix is to validate each entry's header and payload against it->tlv_end inside the iterator.

Risk And Classification

Primary CVSS: v3.1 2 LOW from [email protected]

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

Problem Types: CWE-125 | CWE-125 bounds

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary2LOWCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
3.1CNACVSS2LOWCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mcu-tools Mcuboot affected 0.9.0 2.5.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/mcu-tools/mcuboot/commit/90f4e7c3ebe4cf9a5eb7d981220388ffdefd... [email protected] github.com
github.com/mcu-tools/mcuboot/security/advisories/GHSA-4fp3-3qw2-25jv [email protected] github.com
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