{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "2.0.0"
                  },
                  {
                    "fixed": "2.5.0"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              },
              {
                "range": [
                  {
                    "fixed": "9fb70f00173766d73cdadd82266bd61e4ddd0252"
                  }
                ],
                "source": "REFERENCES_COMMIT"
              }
            ]
          },
          "events": [
            {
              "introduced": "304fd41980ed929533b9f387dde1b463b0be5b90"
            },
            {
              "fixed": "725d63c9d5bc1bb572d802e7a768daf504186daf"
            },
            {
              "fixed": "9fb70f00173766d73cdadd82266bd61e4ddd0252"
            }
          ],
          "repo": "https://github.com/mcu-tools/mcuboot",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-vj6q-r752-fpqv"
  ],
  "database_specific": {
    "cna_assigner": "zephyr",
    "cwe_ids": [
      "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16671.json"
  },
  "details": "split_image_check() in boot/bootutil/src/loader.c declares a fixed uint8_t loader_hash[32] buffer and passes it as the out_hash out-parameter to bootutil_img_validate(). That routine copies IMAGE_HASH_SIZE bytes into out_hash (memcpy(out_hash, hash, IMAGE_HASH_SIZE) in boot/bootutil/src/image_validate.c), where IMAGE_HASH_SIZE is a compile-time constant of 64 for MCUBOOT_SHA512 or 48 for MCUBOOT_SIGN_EC384/SHA-384 (boot/bootutil/include/bootutil/crypto/sha.h). The buffer tracks SHA-256 (32 bytes) while the copy length tracks the configured algorithm, so the write overruns the buffer by 16 or 32 bytes.\n\nThe overflow is only present in a non-default configuration: the legacy Mynewt split-image feature must be compiled (split_go()/split_image_check(), i.e. neither MCUBOOT_DIRECT_XIP nor MCUBOOT_RAM_LOAD), the digest must be larger than 32 bytes (MCUBOOT_SHA512 or MCUBOOT_SIGN_EC384), and MCUBOOT_SIGN_PURE must be off. split_go() is a public API with no caller inside MCUboot; it is invoked from a Mynewt application. In the default SHA-256 build there is no overflow.\n\nThe over-written bytes are the one-way digest of the loader image and the overflow length is fixed at build time, so the contents are not meaningfully attacker-controlled and the size is not attacker-chosen. The realistic impact is bounded, uncontrolled corruption of the bootloader's stack on the split-boot path, manifesting as instability or failed boot in the affected configuration rather than reliable code execution. The fix is to size loader_hash to IMAGE_HASH_SIZE and pass IMAGE_HASH_SIZE as the matching seed length.",
  "id": "CVE-2026-16671",
  "modified": "2026-11-14T02:30:43.977397693Z",
  "published": "2026-11-13T00:23:02.120Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16671.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-vj6q-r752-fpqv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-16671"
    },
    {
      "type": "FIX",
      "url": "https://github.com/mcu-tools/mcuboot/commit/9fb70f00173766d73cdadd82266bd61e4ddd0252"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mcu-tools/mcuboot"
    }
  ],
  "schema_version": "1.9.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Out-of-bounds stack write in MCUboot split-image validation with SHA-384/SHA-512 builds"
}