CVE-2026-18416 (GCVE-0-2026-18416)
Vulnerability from cvelistv5 – Published: 2026-09-28 20:00 – Updated: 2026-09-30 15:28
VLAI
EPSS
VEX
Title
Out-of-bounds read in CoAP well-known-core Uri-Query href matching (match_path_uri)
Summary
The CoAP link-format helper match_path_uri() in subsys/net/lib/coap/coap_link_format.c compares a registered resource path against the URI carried in a Uri-Query href= option. That URI is not NUL terminated, but the inner character loop advanced its index k once per path character without ever testing it against the option length len. When a registered path segment is longer than the supplied URI and the URI is a prefix of it, the loop reads uri[len] and beyond, past the end of the option value.
The path is reached from coap_well_known_core_get_len() and coap_well_known_core_get() via match_queries_resource(), i.e. by any unauthenticated GET /.well-known/core?href=/<prefix> request to a device that serves /.well-known/core (for the CoAP server subsystem, CONFIG_COAP_SERVER_WELL_KNOWN_CORE, default y) and has at least one resource that declares struct coap_core_metadata attributes.
The over-read does not reach the receive buffer. The well-known-core builders parse the query into a stack-local struct coap_option, whose value is a fixed array (value[12], or CONFIG_COAP_EXTENDED_OPTIONS_LEN_VALUE bytes) that the option bytes are copied into, so uri points into that copy. Reading past len therefore reads the unused, uninitialized tail of the array and, when the option fills it, the bytes just past it in the same stack frame. (In the ZoAP library of v1.8.0 to v1.9.x the option value was instead a pointer into the received packet, and the over-read ran past the option inside the packet buffer.)
The impact is bounded. The number of bytes read past the end is limited by the length of the resource path segment, and each additional byte is only read if it happens to equal the next path character, so in practice the over-read is one byte. It also cannot influence the response: returning a match requires the final compared index to be len - 1 or len, both in bounds, so out-of-bounds bytes only ever steer the loop to the next candidate resource. The consequence is undefined behaviour, not information disclosure and not a matching error.
The fix adds a k >= len guard at the top of the inner loop, so every uri[k] dereference is within the option value while still allowing a trailing * wildcard to match a longer path.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-30 15:18 UTC
CWE
- CWE-125 - bounds
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
1.8.0 , < 4.4.2
(semver)
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-18416",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-30T15:18:49.506461Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-30T15:28:20.615Z",
"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/net/lib/coap/coap_link_format.c"
],
"programRoutines": [
{
"name": "coap_well_known_core_get"
},
{
"name": "coap_well_known_core_get_len"
},
{
"name": "match_path_uri"
},
{
"name": "match_queries_resource"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.4.2",
"status": "affected",
"version": "1.8.0",
"versionType": "semver"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "The CoAP link-format helper match_path_uri() in subsys/net/lib/coap/coap_link_format.c compares a registered resource path against the URI carried in a Uri-Query href= option. That URI is not NUL terminated, but the inner character loop advanced its index k once per path character without ever testing it against the option length len. When a registered path segment is longer than the supplied URI and the URI is a prefix of it, the loop reads uri[len] and beyond, past the end of the option value.\n\nThe path is reached from coap_well_known_core_get_len() and coap_well_known_core_get() via match_queries_resource(), i.e. by any unauthenticated GET /.well-known/core?href=/\u003cprefix\u003e request to a device that serves /.well-known/core (for the CoAP server subsystem, CONFIG_COAP_SERVER_WELL_KNOWN_CORE, default y) and has at least one resource that declares struct coap_core_metadata attributes.\n\nThe over-read does not reach the receive buffer. The well-known-core builders parse the query into a stack-local struct coap_option, whose value is a fixed array (value[12], or CONFIG_COAP_EXTENDED_OPTIONS_LEN_VALUE bytes) that the option bytes are copied into, so uri points into that copy. Reading past len therefore reads the unused, uninitialized tail of the array and, when the option fills it, the bytes just past it in the same stack frame. (In the ZoAP library of v1.8.0 to v1.9.x the option value was instead a pointer into the received packet, and the over-read ran past the option inside the packet buffer.)\n\nThe impact is bounded. The number of bytes read past the end is limited by the length of the resource path segment, and each additional byte is only read if it happens to equal the next path character, so in practice the over-read is one byte. It also cannot influence the response: returning a match requires the final compared index to be len - 1 or len, both in bounds, so out-of-bounds bytes only ever steer the loop to the next candidate resource. The consequence is undefined behaviour, not information disclosure and not a matching error.\n\nThe fix adds a k \u003e= len guard at the top of the inner loop, so every uri[k] dereference is within the option value while still allowing a trailing * wildcard to match a longer path."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 3.7,
"baseSeverity": "LOW",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-125",
"description": "bounds",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-28T20:00:02.425Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ef5b303dc88fb5159850623a2b51b590c36fa5bc"
},
{
"name": "GHSA-m3mv-vvm4-h58g",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-m3mv-vvm4-h58g"
}
],
"title": "Out-of-bounds read in CoAP well-known-core Uri-Query href matching (match_path_uri)",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"assignerShortName": "zephyr",
"cveId": "CVE-2026-18416",
"datePublished": "2026-09-28T20:00:02.425Z",
"dateReserved": "2026-07-30T17:54:12.762Z",
"dateUpdated": "2026-09-30T15:28:20.615Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-18416",
"date": "2026-10-03",
"epss": "0.00221",
"percentile": "0.11545"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"subsys/net/lib/coap/coap_link_format.c"
],
"programRoutines": [
{
"name": "coap_well_known_core_get"
},
{
"name": "coap_well_known_core_get_len"
},
{
"name": "match_path_uri"
},
{
"name": "match_queries_resource"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.4.2",
"status": "affected",
"version": "1.8.0",
"versionType": "semver"
}
]
}
],
"source": "vulnerabilities@zephyrproject.org"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "The CoAP link-format helper match_path_uri() in subsys/net/lib/coap/coap_link_format.c compares a registered resource path against the URI carried in a Uri-Query href= option. That URI is not NUL terminated, but the inner character loop advanced its index k once per path character without ever testing it against the option length len. When a registered path segment is longer than the supplied URI and the URI is a prefix of it, the loop reads uri[len] and beyond, past the end of the option value.\n\nThe path is reached from coap_well_known_core_get_len() and coap_well_known_core_get() via match_queries_resource(), i.e. by any unauthenticated GET /.well-known/core?href=/\u003cprefix\u003e request to a device that serves /.well-known/core (for the CoAP server subsystem, CONFIG_COAP_SERVER_WELL_KNOWN_CORE, default y) and has at least one resource that declares struct coap_core_metadata attributes.\n\nThe over-read does not reach the receive buffer. The well-known-core builders parse the query into a stack-local struct coap_option, whose value is a fixed array (value[12], or CONFIG_COAP_EXTENDED_OPTIONS_LEN_VALUE bytes) that the option bytes are copied into, so uri points into that copy. Reading past len therefore reads the unused, uninitialized tail of the array and, when the option fills it, the bytes just past it in the same stack frame. (In the ZoAP library of v1.8.0 to v1.9.x the option value was instead a pointer into the received packet, and the over-read ran past the option inside the packet buffer.)\n\nThe impact is bounded. The number of bytes read past the end is limited by the length of the resource path segment, and each additional byte is only read if it happens to equal the next path character, so in practice the over-read is one byte. It also cannot influence the response: returning a match requires the final compared index to be len - 1 or len, both in bounds, so out-of-bounds bytes only ever steer the loop to the next candidate resource. The consequence is undefined behaviour, not information disclosure and not a matching error.\n\nThe fix adds a k \u003e= len guard at the top of the inner loop, so every uri[k] dereference is within the option value while still allowing a trailing * wildcard to match a longer path."
}
],
"id": "CVE-2026-18416",
"lastModified": "2026-09-30T16:17:12.250",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 3.7,
"baseSeverity": "LOW",
"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:L",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 1.4,
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-18416",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-30T15:18:49.506461Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-28T21:17:17.560",
"references": [
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ef5b303dc88fb5159850623a2b51b590c36fa5bc"
},
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-m3mv-vvm4-h58g"
}
],
"sourceIdentifier": "vulnerabilities@zephyrproject.org",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-125"
}
],
"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-18416",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-30T15:18:49.506461Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-30T15:27:31.086Z",
"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/net/lib/coap/coap_link_format.c"
],
"programRoutines": [
{
"name": "coap_well_known_core_get"
},
{
"name": "coap_well_known_core_get_len"
},
{
"name": "match_path_uri"
},
{
"name": "match_queries_resource"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.4.2",
"status": "affected",
"version": "1.8.0",
"versionType": "semver"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "The CoAP link-format helper match_path_uri() in subsys/net/lib/coap/coap_link_format.c compares a registered resource path against the URI carried in a Uri-Query href= option. That URI is not NUL terminated, but the inner character loop advanced its index k once per path character without ever testing it against the option length len. When a registered path segment is longer than the supplied URI and the URI is a prefix of it, the loop reads uri[len] and beyond, past the end of the option value.\n\nThe path is reached from coap_well_known_core_get_len() and coap_well_known_core_get() via match_queries_resource(), i.e. by any unauthenticated GET /.well-known/core?href=/\u003cprefix\u003e request to a device that serves /.well-known/core (for the CoAP server subsystem, CONFIG_COAP_SERVER_WELL_KNOWN_CORE, default y) and has at least one resource that declares struct coap_core_metadata attributes.\n\nThe over-read does not reach the receive buffer. The well-known-core builders parse the query into a stack-local struct coap_option, whose value is a fixed array (value[12], or CONFIG_COAP_EXTENDED_OPTIONS_LEN_VALUE bytes) that the option bytes are copied into, so uri points into that copy. Reading past len therefore reads the unused, uninitialized tail of the array and, when the option fills it, the bytes just past it in the same stack frame. (In the ZoAP library of v1.8.0 to v1.9.x the option value was instead a pointer into the received packet, and the over-read ran past the option inside the packet buffer.)\n\nThe impact is bounded. The number of bytes read past the end is limited by the length of the resource path segment, and each additional byte is only read if it happens to equal the next path character, so in practice the over-read is one byte. It also cannot influence the response: returning a match requires the final compared index to be len - 1 or len, both in bounds, so out-of-bounds bytes only ever steer the loop to the next candidate resource. The consequence is undefined behaviour, not information disclosure and not a matching error.\n\nThe fix adds a k \u003e= len guard at the top of the inner loop, so every uri[k] dereference is within the option value while still allowing a trailing * wildcard to match a longer path."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 3.7,
"baseSeverity": "LOW",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-125",
"description": "bounds",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-28T20:00:02.425Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ef5b303dc88fb5159850623a2b51b590c36fa5bc"
},
{
"name": "GHSA-m3mv-vvm4-h58g",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-m3mv-vvm4-h58g"
}
],
"title": "Out-of-bounds read in CoAP well-known-core Uri-Query href matching (match_path_uri)",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"assignerShortName": "zephyr",
"cveId": "CVE-2026-18416",
"datePublished": "2026-09-28T20:00:02.425Z",
"dateReserved": "2026-07-30T17:54:12.762Z",
"dateUpdated": "2026-09-30T15:28:20.615Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
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.
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.
Loading…