CVE-2026-76787 (GCVE-0-2026-76787)
Vulnerability from cvelistv5 – Published: 2026-10-19 20:39 – Updated: 2026-10-20 18:08
VLAI
EPSS
VEX
Title
NULL pointer dereference in the UpdateHub FOTA client when probe metadata omits sha256sum
Summary
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 — json_obj_parse() returns a bitmask of the fields it actually decoded and never fails on a missing one — 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.
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 — the default — 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.
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 — MMU-based architectures, builds with CONFIG_NULL_POINTER_EXCEPTION_DETECTION_DWT/_MPU/_PMP, TrustZone non-secure images, and SoCs such as nRF54L whose 0x0–0x400 window is unmapped — 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.
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.
Severity
5.9 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-20 18:04 UTC
CWE
- CWE-476 - memory-safety
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
2.4.0 , < 4.5.0
(semver)
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-76787",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-20T18:04:36.017568Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-20T18:08:01.790Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/mgmt/updatehub/updatehub.c"
],
"programRoutines": [
{
"name": "z_impl_updatehub_probe"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.5.0",
"status": "affected",
"version": "2.4.0",
"versionType": "semver"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "The UpdateHub firmware-over-the-air client parses the CoAP probe response with Zephyr\u0027s 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.\n\nThe 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.\n\nThe 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\u0027s 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.\n\nThe 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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-476",
"description": "memory-safety",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-19T20:39:20.425Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/6fc4f27a74021b52c509e4f7912d68145dfa7728"
},
{
"name": "GHSA-82gq-cmqw-xgx2",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-82gq-cmqw-xgx2"
}
],
"title": "NULL pointer dereference in the UpdateHub FOTA client when probe metadata omits sha256sum",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"assignerShortName": "zephyr",
"cveId": "CVE-2026-76787",
"datePublished": "2026-10-19T20:39:20.425Z",
"dateReserved": "2026-08-19T17:53:24.899Z",
"dateUpdated": "2026-10-20T18:08:01.790Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-76787",
"date": "2026-10-29",
"epss": "0.00362",
"percentile": "0.2999"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/mgmt/updatehub/updatehub.c"
],
"programRoutines": [
{
"name": "z_impl_updatehub_probe"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.5.0",
"status": "affected",
"version": "2.4.0",
"versionType": "semver"
}
]
}
],
"source": "vulnerabilities@zephyrproject.org"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "The UpdateHub firmware-over-the-air client parses the CoAP probe response with Zephyr\u0027s 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.\n\nThe 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.\n\nThe 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\u0027s 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.\n\nThe 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."
}
],
"id": "CVE-2026-76787",
"lastModified": "2026-10-20T19:59:00.607",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 3.6,
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-76787",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-20T18:04:36.017568Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-10-19T21:18:01.230",
"references": [
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/6fc4f27a74021b52c509e4f7912d68145dfa7728"
},
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-82gq-cmqw-xgx2"
}
],
"sourceIdentifier": "vulnerabilities@zephyrproject.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-476"
}
],
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-76787",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-20T18:04:36.017568Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-20T18:07:50.690Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/mgmt/updatehub/updatehub.c"
],
"programRoutines": [
{
"name": "z_impl_updatehub_probe"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.5.0",
"status": "affected",
"version": "2.4.0",
"versionType": "semver"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "The UpdateHub firmware-over-the-air client parses the CoAP probe response with Zephyr\u0027s 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.\n\nThe 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.\n\nThe 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\u0027s 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.\n\nThe 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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-476",
"description": "memory-safety",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-19T20:39:20.425Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/6fc4f27a74021b52c509e4f7912d68145dfa7728"
},
{
"name": "GHSA-82gq-cmqw-xgx2",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-82gq-cmqw-xgx2"
}
],
"title": "NULL pointer dereference in the UpdateHub FOTA client when probe metadata omits sha256sum",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"assignerShortName": "zephyr",
"cveId": "CVE-2026-76787",
"datePublished": "2026-10-19T20:39:20.425Z",
"dateReserved": "2026-08-19T17:53:24.899Z",
"dateUpdated": "2026-10-20T18:08:01.790Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.