{"api_version":"1","generated_at":"2026-11-13T05:20:30+00:00","cve":"CVE-2026-16659","urls":{"html":"https://cve.report/CVE-2026-16659","api":"https://cve.report/api/cve/CVE-2026-16659.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-16659","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-16659"},"summary":{"title":"Pre-authentication NULL pointer dereference in MCUboot serial-recovery image upload (encrypted-image builds)","description":"MCUboot's serial-recovery image-upload handler bs_upload() in boot/boot_serial/src/boot_serial.c declares const struct flash_area *fap = NULL and assigns it only via flash_area_open() part-way through the function. Two early validation failures (goto out_invalid_data) — a CBOR map that fails to decode, or an upload packet missing the off/data members — branch past the open while fap is still NULL, then fall into the shared epilogue. In MCUBOOT_ENC_IMAGES builds that epilogue unconditionally calls boot_handle_enc_fw(fap), which reaches boot_image_load_header() and flash_area_read() and dereferences the NULL flash_area.\n\nThe defect is reachable pre-authentication: the trigger is the very first serial-recovery upload command carrying a malformed payload. The guarding conditions are default-true on a fresh recovery session — img_num, curr_off and img_size are zero-initialized statics, so curr_off == img_size and the primary-slot test both hold. It requires a non-default build: encrypted images (MCUBOOT_ENC_IMAGES / Zephyr CONFIG_BOOT_ENCRYPT_IMAGE) together with an active serial-recovery transport, on the Zephyr or Mynewt port (the two that build both boot/boot_serial/src/boot_serial.c and boot_serial_encryption.c with MCUBOOT_ENC_IMAGES).\n\nThe impact is a transient denial of service of the bootloader during recovery. fap is a hard NULL rather than an attacker-controlled value, so there is no memory-corruption or information-leak primitive and image authentication is unaffected. Whether the dereference faults is platform-dependent — on targets where address 0x0 is mapped readable flash the read merely returns an error and execution continues, while targets that trap NULL (MPU / null-pointer-exception detection) take a hard fault. Because serial recovery is unauthenticated by design and already permits the console attacker to write the secondary slot, the added capability is only a low-value transient crash.\n\nThe related unconditional flash_area_close(fap) call in the same epilogue is a safe no-op on the ports that reach it, so it does not contribute to the dereference.\n\nThe affected ports are the Zephyr port — boot/zephyr/CMakeLists.txt compiles boot_serial.c under CONFIG_MCUBOOT_SERIAL and boot_serial_encryption.c under CONFIG_BOOT_ENCRYPT_IMAGE — and the Mynewt port, whose mcuboot_config.h defines MCUBOOT_SERIAL unconditionally and MCUBOOT_ENC_IMAGES under any BOOTUTIL_ENCRYPT_ syscfg, with boot/boot_serial/pkg.yml declaring no explicit source list so the whole directory is built. The Espressif port is not affected**: it compiles boot_serial.c but not boot_serial_encryption.c, and defines no MCUBOOT_ENC_IMAGES, so the #ifdef MCUBOOT_ENC_IMAGES block containing the call is preprocessed away. The NuttX, Cypress and Mbed ports do not build boot_serial.c at all.","state":"PUBLISHED","assigner":"zephyr","published_at":"2026-11-13 02:18:56","updated_at":"2026-11-13 02:18:56"},"problem_types":["CWE-476","CWE-476 memory-safety"],"metrics":[{"version":"3.1","source":"vulnerabilities@zephyrproject.org","type":"Secondary","score":"4","severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","baseScore":4,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"4","severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","data":{"baseScore":4,"baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}}],"references":[{"url":"https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-777r-3chm-p78c","name":"https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-777r-3chm-p78c","refsource":"vulnerabilities@zephyrproject.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/mcu-tools/mcuboot/commit/400f9a7242641655948b08acac19932f56d9881f","name":"https://github.com/mcu-tools/mcuboot/commit/400f9a7242641655948b08acac19932f56d9881f","refsource":"vulnerabilities@zephyrproject.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-16659","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16659","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"mcu-tools","product":"mcuboot","version":"affected 2.0.0 2.5.0 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://github.com/mcu-tools/mcuboot","defaultStatus":"unaffected","packageName":"mcuboot","product":"mcuboot","programFiles":["boot/boot_serial/src/boot_serial.c","boot/boot_serial/src/boot_serial_encryption.c"],"programRoutines":[{"name":"boot_handle_enc_fw"},{"name":"bs_upload"}],"vendor":"mcu-tools","versions":[{"lessThan":"2.5.0","status":"affected","version":"2.0.0","versionType":"semver"}]}],"descriptions":[{"lang":"en","value":"MCUboot's serial-recovery image-upload handler bs_upload() in boot/boot_serial/src/boot_serial.c declares const struct flash_area *fap = NULL and assigns it only via flash_area_open() part-way through the function. Two early validation failures (goto out_invalid_data) — a CBOR map that fails to decode, or an upload packet missing the off/data members — branch past the open while fap is still NULL, then fall into the shared epilogue. In MCUBOOT_ENC_IMAGES builds that epilogue unconditionally calls boot_handle_enc_fw(fap), which reaches boot_image_load_header() and flash_area_read() and dereferences the NULL flash_area.\n\nThe defect is reachable pre-authentication: the trigger is the very first serial-recovery upload command carrying a malformed payload. The guarding conditions are default-true on a fresh recovery session — img_num, curr_off and img_size are zero-initialized statics, so curr_off == img_size and the primary-slot test both hold. It requires a non-default build: encrypted images (MCUBOOT_ENC_IMAGES / Zephyr CONFIG_BOOT_ENCRYPT_IMAGE) together with an active serial-recovery transport, on the Zephyr or Mynewt port (the two that build both boot/boot_serial/src/boot_serial.c and boot_serial_encryption.c with MCUBOOT_ENC_IMAGES).\n\nThe impact is a transient denial of service of the bootloader during recovery. fap is a hard NULL rather than an attacker-controlled value, so there is no memory-corruption or information-leak primitive and image authentication is unaffected. Whether the dereference faults is platform-dependent — on targets where address 0x0 is mapped readable flash the read merely returns an error and execution continues, while targets that trap NULL (MPU / null-pointer-exception detection) take a hard fault. Because serial recovery is unauthenticated by design and already permits the console attacker to write the secondary slot, the added capability is only a low-value transient crash.\n\nThe related unconditional flash_area_close(fap) call in the same epilogue is a safe no-op on the ports that reach it, so it does not contribute to the dereference.\n\nThe affected ports are the Zephyr port — boot/zephyr/CMakeLists.txt compiles boot_serial.c under CONFIG_MCUBOOT_SERIAL and boot_serial_encryption.c under CONFIG_BOOT_ENCRYPT_IMAGE — and the Mynewt port, whose mcuboot_config.h defines MCUBOOT_SERIAL unconditionally and MCUBOOT_ENC_IMAGES under any BOOTUTIL_ENCRYPT_ syscfg, with boot/boot_serial/pkg.yml declaring no explicit source list so the whole directory is built. The Espressif port is not affected**: it compiles boot_serial.c but not boot_serial_encryption.c, and defines no MCUBOOT_ENC_IMAGES, so the #ifdef MCUBOOT_ENC_IMAGES block containing the call is preprocessed away. The NuttX, Cypress and Mbed ports do not build boot_serial.c at all."}],"metrics":[{"cvssV3_1":{"baseScore":4,"baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-476","description":"memory-safety","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-11-13T00:23:03.881Z","orgId":"e2e69745-5e70-4e92-8431-deb5529a81ad","shortName":"zephyr"},"references":[{"name":"Fix commit","tags":["patch"],"url":"https://github.com/mcu-tools/mcuboot/commit/400f9a7242641655948b08acac19932f56d9881f"},{"name":"GHSA-777r-3chm-p78c","url":"https://github.com/mcu-tools/mcuboot/security/advisories/GHSA-777r-3chm-p78c"}],"title":"Pre-authentication NULL pointer dereference in MCUboot serial-recovery image upload (encrypted-image builds)","x_generator":{"engine":"cvelib 1.8.0"}}},"cveMetadata":{"assignerOrgId":"e2e69745-5e70-4e92-8431-deb5529a81ad","assignerShortName":"zephyr","cveId":"CVE-2026-16659","datePublished":"2026-11-13T00:23:03.881Z","dateReserved":"2026-07-22T19:41:19.883Z","dateUpdated":"2026-11-13T00:23:03.881Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-11-13 02:18:56","lastModifiedDate":"2026-11-13 02:18:56","problem_types":["CWE-476","CWE-476 memory-safety"],"metrics":{"cvssMetricV31":[{"source":"vulnerabilities@zephyrproject.org","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","baseScore":4,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW"},"exploitabilityScore":2.5,"impactScore":1.4}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"16659","Ordinal":"1","Title":"Pre-authentication NULL pointer dereference in MCUboot serial-re","CVE":"CVE-2026-16659","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"16659","Ordinal":"1","NoteData":"MCUboot's serial-recovery image-upload handler bs_upload() in boot/boot_serial/src/boot_serial.c declares const struct flash_area *fap = NULL and assigns it only via flash_area_open() part-way through the function. Two early validation failures (goto out_invalid_data) — a CBOR map that fails to decode, or an upload packet missing the off/data members — branch past the open while fap is still NULL, then fall into the shared epilogue. In MCUBOOT_ENC_IMAGES builds that epilogue unconditionally calls boot_handle_enc_fw(fap), which reaches boot_image_load_header() and flash_area_read() and dereferences the NULL flash_area.\n\nThe defect is reachable pre-authentication: the trigger is the very first serial-recovery upload command carrying a malformed payload. The guarding conditions are default-true on a fresh recovery session — img_num, curr_off and img_size are zero-initialized statics, so curr_off == img_size and the primary-slot test both hold. It requires a non-default build: encrypted images (MCUBOOT_ENC_IMAGES / Zephyr CONFIG_BOOT_ENCRYPT_IMAGE) together with an active serial-recovery transport, on the Zephyr or Mynewt port (the two that build both boot/boot_serial/src/boot_serial.c and boot_serial_encryption.c with MCUBOOT_ENC_IMAGES).\n\nThe impact is a transient denial of service of the bootloader during recovery. fap is a hard NULL rather than an attacker-controlled value, so there is no memory-corruption or information-leak primitive and image authentication is unaffected. Whether the dereference faults is platform-dependent — on targets where address 0x0 is mapped readable flash the read merely returns an error and execution continues, while targets that trap NULL (MPU / null-pointer-exception detection) take a hard fault. Because serial recovery is unauthenticated by design and already permits the console attacker to write the secondary slot, the added capability is only a low-value transient crash.\n\nThe related unconditional flash_area_close(fap) call in the same epilogue is a safe no-op on the ports that reach it, so it does not contribute to the dereference.\n\nThe affected ports are the Zephyr port — boot/zephyr/CMakeLists.txt compiles boot_serial.c under CONFIG_MCUBOOT_SERIAL and boot_serial_encryption.c under CONFIG_BOOT_ENCRYPT_IMAGE — and the Mynewt port, whose mcuboot_config.h defines MCUBOOT_SERIAL unconditionally and MCUBOOT_ENC_IMAGES under any BOOTUTIL_ENCRYPT_ syscfg, with boot/boot_serial/pkg.yml declaring no explicit source list so the whole directory is built. The Espressif port is not affected**: it compiles boot_serial.c but not boot_serial_encryption.c, and defines no MCUBOOT_ENC_IMAGES, so the #ifdef MCUBOOT_ENC_IMAGES block containing the call is preprocessed away. The NuttX, Cypress and Mbed ports do not build boot_serial.c at all.","Type":"Description","Title":"Pre-authentication NULL pointer dereference in MCUboot serial-re"}]}}}