The UpdateHub firmware-over-the-air client parses the CoAP probe response with Zephyr’s JSON library in z_impl_updatehub_probe() (subsys\/mgmt\/updatehub\/updatehub.c). The decoder treats every descriptor field as optional \u2014 json_obj_parse() returns a bitmask of the fields it actually decoded and never fails on a missing one \u2014 so a response that omits the “sha256sum” string leaves the corresponding const char * in the zero-initialised struct resp_probe_any_boards \/ struct resp_probe_some_boards at NULL. Both metadata branches then computed sha256size = strlen(…objects.sha256sum) + 1 before any validation, dereferencing that NULL pointer; the SHA256_HEX_DIGEST_SIZE test that follows operates on a value the bad read has already produced and cannot prevent it.<\/p>\n
The metadata is supplied entirely by the network peer: probe_cb() accepts the datagram, runs coap_packet_parse() and copies the payload with no token matching and no cryptographic check. With CONFIG_UPDATEHUB_DTLS unset \u2014 the default \u2014 start_coap_client() uses plain CoAP over UDP on port 5683 with no peer authentication and resolves the server via unauthenticated DNS, so an on-path attacker, a DNS spoofer, or an off-path attacker who wins the race with a forged source address can deliver the malformed metadata. A probe response as simple as “objects”:[[{}],[{}]] suffices, and no user interaction is required because updatehub_autohandler() polls on CONFIG_UPDATEHUB_POLL_INTERVAL. When CONFIG_UPDATEHUB_DTLS=y the trigger narrows to a malicious or compromised update server.<\/p>\n
The primitive is a read at address zero, not a write, so the impact is availability only. On targets where the low address range is unmapped or protected \u2014 MMU-based architectures, builds with CONFIG_NULL_POINTER_EXCEPTION_DETECTION_DWT\/_MPU\/_PMP, TrustZone non-secure images, and SoCs such as nRF54L whose 0x0\u20130x400 window is unmapped \u2014 the load faults and Zephyr’s default fatal handler halts the system, giving a remotely re-triggerable denial of service on every poll. On classic Cortex-M targets where the vector table is readable at address zero the walk usually terminates immediately and the request is rejected by the length check, so the outcome is configuration- and SoC-dependent. There is no memory write, and the copied bytes are only compared against the locally computed image hash, so there is no information-disclosure channel.<\/p>\n
The fix adds an explicit sha256sum == NULL test that returns UPDATEHUB_METADATA_ERROR ahead of the strlen() in both metadata branches. Debug builds (CONFIG_UPDATEHUB_LOG_LEVEL=4) still format the same pointers with %s in a LOG_DBG() loop that runs before the new checks, so that variant remains in debug configurations only.<\/p>\n","protected":false},"excerpt":{"rendered":"
The UpdateHub firmware-over-the-air client parses the CoAP probe response with Zephyr’s JSON library in z_impl_updatehub_probe() (subsys\/mgmt\/updatehub\/updatehub.c). The decoder treats every descripto<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-41764","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/41764","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41764"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41764"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41764"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}