CVE-2026-16515
net_icmpv6_send_error() in subsys/net/ip/icmpv6.c implemented only one of the three RFC 4443 section 2.4 suppression rules (do not answer an ICMPv6 error with an ICMPv6 error). It did not check whether the triggering packet's source address identifies a single node (rule e.6) or whether the packet was sent to a multicast destination (rule e.3, whose only exceptions are Packet Too Big and Parameter Problem Code 2). Of the five call sites, only the port-unreachable path in subsys/net/ip/connection.c carried an equivalent guard of its own; the extension-header, unknown-next-header and fragmentation paths in subsys/net/ip/ipv6.c and subsys/net/ip/ipv6_fragment.c had none.
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An unauthenticated attacker with access to the same link can exploit this in two ways. Sending a single IPv6 packet to the link-local all-nodes group ff02::1 carrying an unrecognized next-header value, with the source address spoofed to a chosen victim, causes every Zephyr node on the link to emit an ICMPv6 Parameter Problem message to that victim — a reflector with an amplification factor equal to the number of nodes. Alternatively, sending a unicast packet whose source address is a multicast address causes the node to transmit its ICMPv6 error to that multicast address, turning one unicast packet into a link-flooded multicast frame. Packets addressed to ff02::1 are accepted unconditionally by ipv6_input(), and no check rejects a multicast source address, so no special configuration is required.
The impact is degraded availability of the shared link and of the reflection victim, together with the ability for the attacker to hide its own address behind the responding nodes. The effect is amplified on constrained mesh links such as 802.15.4/Thread, where link-local multicast is flooded hop by hop. There is no memory-safety consequence: the error packet itself is well formed, it is simply emitted in cases where the protocol forbids it.
The fix adds both suppression checks at the single choke point in net_icmpv6_send_error(), before any reply packet is allocated, preserving the RFC-mandated exceptions for NET_ICMPV6_PACKET_TOO_BIG and Parameter Problem Code 2. Note that the IPv4 counterpart net_icmpv4_send_error() in subsys/net/ip/icmpv4.c still checks only for a broadcast destination and retains an equivalent gap for multicast destinations and non-unique sources.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
- Puntuación base: 4.7
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement75 % - Impacto principal
T1499.004Application or System Exploitationimpact85 % - Impacto secundario
T1090Proxycommand and control60 %
Explotación de servicio remoto (IPv6 en red adyacente, sin autenticación). Impacto primario: DoS de disponibilidad mediante amplificación de ICMPv6 reflejado. Secundario: enmascaramiento de origen del atacante.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-406
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-16515",
"cveTags": [],
"metrics": {
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"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-16515",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-09-18T16:25:27.449454Z"
}
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"cvssMetricV31": [
{
"type": "Secondary",
"source": "vulnerabilities@zephyrproject.org",
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"version": "3.1",
"baseScore": 4.7,
"attackVector": "ADJACENT_NETWORK",
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "LOW",
"privilegesRequired": "NONE",
"confidentialityImpact": "NONE"
},
"impactScore": 1.4,
"exploitabilityScore": 2.8
}
]
},
"affected": [
{
"source": "vulnerabilities@zephyrproject.org",
"affectedData": [
{
"vendor": "zephyrproject",
"product": "zephyr",
"versions": [
{
"status": "affected",
"version": "1.14.0",
"lessThan": "4.4.2",
"versionType": "semver"
}
],
"packageName": "zephyr",
"programFiles": [
"subsys/net/ip/icmpv6.c"
],
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "net_icmpv6_send_error"
}
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}
],
"published": "2026-09-18T15:17:05.897",
"references": [
{
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ba4247b24ddd3a5360b617e3ca17131ca9e8026a",
"source": "vulnerabilities@zephyrproject.org"
},
{
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-v5vw-m78m-h46g",
"source": "vulnerabilities@zephyrproject.org"
}
],
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"type": "Secondary",
"source": "vulnerabilities@zephyrproject.org",
"description": [
{
"lang": "en",
"value": "CWE-406"
}
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"descriptions": [
{
"lang": "en",
"value": "net_icmpv6_send_error() in subsys/net/ip/icmpv6.c implemented only one of the three RFC 4443 section 2.4 suppression rules (do not answer an ICMPv6 error with an ICMPv6 error). It did not check whether the triggering packet's source address identifies a single node (rule e.6) or whether the packet was sent to a multicast destination (rule e.3, whose only exceptions are Packet Too Big and Parameter Problem Code 2). Of the five call sites, only the port-unreachable path in subsys/net/ip/connection.c carried an equivalent guard of its own; the extension-header, unknown-next-header and fragmentation paths in subsys/net/ip/ipv6.c and subsys/net/ip/ipv6_fragment.c had none.\n\nAn unauthenticated attacker with access to the same link can exploit this in two ways. Sending a single IPv6 packet to the link-local all-nodes group ff02::1 carrying an unrecognized next-header value, with the source address spoofed to a chosen victim, causes every Zephyr node on the link to emit an ICMPv6 Parameter Problem message to that victim — a reflector with an amplification factor equal to the number of nodes. Alternatively, sending a unicast packet whose source address is a multicast address causes the node to transmit its ICMPv6 error to that multicast address, turning one unicast packet into a link-flooded multicast frame. Packets addressed to ff02::1 are accepted unconditionally by ipv6_input(), and no check rejects a multicast source address, so no special configuration is required.\n\nThe impact is degraded availability of the shared link and of the reflection victim, together with the ability for the attacker to hide its own address behind the responding nodes. The effect is amplified on constrained mesh links such as 802.15.4/Thread, where link-local multicast is flooded hop by hop. There is no memory-safety consequence: the error packet itself is well formed, it is simply emitted in cases where the protocol forbids it.\n\nThe fix adds both suppression checks at the single choke point in net_icmpv6_send_error(), before any reply packet is allocated, preserving the RFC-mandated exceptions for NET_ICMPV6_PACKET_TOO_BIG and Parameter Problem Code 2. Note that the IPv4 counterpart net_icmpv4_send_error() in subsys/net/ip/icmpv4.c still checks only for a broadcast destination and retains an equivalent gap for multicast destinations and non-unique sources."
}
],
"lastModified": "2026-09-18T19:11:57.760",
"sourceIdentifier": "vulnerabilities@zephyrproject.org"
}