{"affected":[{"defaultStatus":"unaffected","ecosystem":"https://github.com/mcu-tools/mcuboot","packageName":"mcuboot","product":"mcuboot","source":"CNA: zephyr","vendor":"mcu-tools","versions":[{"lessThan":"2.5.0","status":"affected","version":"0.9.0","versionType":"semver"}]}],"cveId":"CVE-2026-127915","cwes":["CWE-125"],"description":"The 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.\n\nThe 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.\n\nThe 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.","epss":null,"exploits":[],"kev":null,"metrics":[{"score":2,"severity":"low","source":"CNA: zephyr","vector":"CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}],"modifiedAt":1794529387449,"publishedAt":1794529387449,"references":[{"source":"CNA: zephyr","tags":["patch"],"url":"https://github.com/mcu-tools/mcuboot/commit/90f4e7c3ebe4cf9a5eb7d981220388ffdefd6d19"},{"source":"CNA: zephyr","tags":[],"url":"https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-4fp3-3qw2-25jv"}],"remediation":[{"kind":"fix","source":"CNA: zephyr","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/mcu-tools/mcuboot/commit/90f4e7c3ebe4cf9a5eb7d981220388ffdefd6d19"}],"revision":"4649e76bd594a65fcc9c98cecc9612b4d49a98cd8b050bda5901c50081e2a889","sources":[{"modifiedAt":1794529387449,"name":"CNA: zephyr","retrievedAt":1794532170363,"url":"https://www.cve.org/CVERecord?id=CVE-2026-127915"}],"ssvc":null,"status":"published","title":"TLV iterator does not bound each entry against the declared TLV area in MCUboot bootutil","updatedAt":1794532170363}