CVE-2026-18417 (GCVE-0-2026-18417)
Vulnerability from cvelistv5 – Published: 2026-09-28 23:25 – Updated: 2026-09-28 23:25
VLAI
EPSS
VEX
Title
Wild pointer dereference in Zephyr BSD sockets when a TCP listening socket reports an asynchronous error
Summary
The native BSD-socket layer recorded a pending asynchronous socket error by type-punning it into struct net_context's void user_data field (ctx->user_data = INT_TO_POINTER(-status) in zsock_accepted_cb(), zsock_received_cb(), zsock_connected_cb() and zsock_close_ctx() in subsys/net/lib/sockets/sockets_inet.c), reading it back with POINTER_TO_INT(). That same field is owned by the network stack for listening TCP contexts: net_tcp_accept() stores the parent context pointer there and the TCP core passes it back to the registered accept callback. A failed accept therefore left a small integer (an errno value) where the stack expected a struct net_context .
When the network interface carrying a listening TCP socket goes down, close_tcp_conn() in subsys/net/ip/tcp.c invokes the accept callback with -ENETDOWN and the context's user_data. In v4.3.0 the callback was not disarmed afterwards, so a second interface-down event forwarded the previously stored errno to zsock_accepted_cb(), which dereferenced it as the parent context and performed several stores through it (sock_set_error()'s read-modify-write of socket_data, k_fifo_cancel_wait(&parent->recv_q)) — the crash described in the fix's commit message. v4.3.1 and v4.4.x carry a later change clearing conn->accept_cb after the error callback (269cb8823d3 on the v4.3 branch, 913fae5169425550f2364655298fceb79b320066 on main), which closes that repeat path; on those releases the poisoned cookie remains reachable only by a narrower race, a handshake completing alongside the interface-down still passing the stale cookie to k_fifo_put(&parent->accept_q, ...), and by getsockopt(SO_ERROR), which reads the field back unconditionally.
On v4.3.0 an application that keeps a listening TCP socket open across repeated link-down events is sufficient to reach the defect; the triggering condition is a network-interface state change, not attacker-supplied packet data, so the practical attacker is one able to force the link down repeatedly (for example an adjacent attacker disrupting a wireless link) or one with local/physical access. Because both the faulting address and the stored data are fixed small constants derived from the errno value, the outcome is a wild-pointer access leading to a kernel fatal error — a denial of service (device crash or reset) rather than an attacker-directed memory corruption.
The fix stores the pending error in a dedicated net_context.sock_error field and converts every producer and consumer to sock_set_error()/sock_get_error(), leaving user_data untouched. As a side effect it also stops getsockopt(SO_ERROR) — which is evaluated unconditionally — from returning the kernel address held in user_data to a userspace application.
Severity
6.5 (Medium)
CWE
- CWE-843 - memory-safety
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
4.3.0 , < 4.4.2
(semver)
|
guessed |
{
"containers": {
"cna": {
"affected": [
{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"include/zephyr/net/net_context.h",
"subsys/net/lib/sockets/sockets_inet.c",
"subsys/net/lib/sockets/sockets_internal.h"
],
"programRoutines": [
{
"name": "close_tcp_conn"
},
{
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}
],
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}
],
"metrics": [
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"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"format": "CVSS"
}
],
"problemTypes": [
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"descriptions": [
{
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"description": "memory-safety",
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"providerMetadata": {
"dateUpdated": "2026-09-28T23:25:23.903Z",
"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
},
"references": [
{
"name": "Fix commit",
"tags": [
"patch"
],
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ef370a57d07637aaee8cec7b0bcebf4002ac8f54"
},
{
"name": "GHSA-p8r8-8mw8-3wf9",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-p8r8-8mw8-3wf9"
}
],
"title": "Wild pointer dereference in Zephyr BSD sockets when a TCP listening socket reports an asynchronous error",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
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"assignerShortName": "zephyr",
"cveId": "CVE-2026-18417",
"datePublished": "2026-09-28T23:25:23.903Z",
"dateReserved": "2026-07-30T17:54:13.939Z",
"dateUpdated": "2026-09-28T23:25:23.903Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-18417",
"date": "2026-09-29",
"epss": "0.00175",
"percentile": "0.06192"
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"nvd": {
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"affected": [
{
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{
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"defaultStatus": "unaffected",
"packageName": "zephyr",
"product": "zephyr",
"programFiles": [
"include/zephyr/net/net_context.h",
"subsys/net/lib/sockets/sockets_inet.c",
"subsys/net/lib/sockets/sockets_internal.h"
],
"programRoutines": [
{
"name": "close_tcp_conn"
},
{
"name": "zsock_accepted_cb"
}
],
"vendor": "zephyrproject",
"versions": [
{
"lessThan": "4.4.2",
"status": "affected",
"version": "4.3.0",
"versionType": "semver"
}
]
}
],
"source": "vulnerabilities@zephyrproject.org"
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"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "The native BSD-socket layer recorded a pending asynchronous socket error by type-punning it into struct net_context\u0027s void user_data field (ctx-\u003euser_data = INT_TO_POINTER(-status) in zsock_accepted_cb(), zsock_received_cb(), zsock_connected_cb() and zsock_close_ctx() in subsys/net/lib/sockets/sockets_inet.c), reading it back with POINTER_TO_INT(). That same field is owned by the network stack for listening TCP contexts: net_tcp_accept() stores the parent context pointer there and the TCP core passes it back to the registered accept callback. A failed accept therefore left a small integer (an errno value) where the stack expected a struct net_context .\n\nWhen the network interface carrying a listening TCP socket goes down, close_tcp_conn() in subsys/net/ip/tcp.c invokes the accept callback with -ENETDOWN and the context\u0027s user_data. In v4.3.0 the callback was not disarmed afterwards, so a second interface-down event forwarded the previously stored errno to zsock_accepted_cb(), which dereferenced it as the parent context and performed several stores through it (sock_set_error()\u0027s read-modify-write of socket_data, k_fifo_cancel_wait(\u0026parent-\u003erecv_q)) \u2014 the crash described in the fix\u0027s commit message. v4.3.1 and v4.4.x carry a later change clearing conn-\u003eaccept_cb after the error callback (269cb8823d3 on the v4.3 branch, 913fae5169425550f2364655298fceb79b320066 on main), which closes that repeat path; on those releases the poisoned cookie remains reachable only by a narrower race, a handshake completing alongside the interface-down still passing the stale cookie to k_fifo_put(\u0026parent-\u003eaccept_q, ...), and by getsockopt(SO_ERROR), which reads the field back unconditionally.\n\nOn v4.3.0 an application that keeps a listening TCP socket open across repeated link-down events is sufficient to reach the defect; the triggering condition is a network-interface state change, not attacker-supplied packet data, so the practical attacker is one able to force the link down repeatedly (for example an adjacent attacker disrupting a wireless link) or one with local/physical access. Because both the faulting address and the stored data are fixed small constants derived from the errno value, the outcome is a wild-pointer access leading to a kernel fatal error \u2014 a denial of service (device crash or reset) rather than an attacker-directed memory corruption.\n\nThe fix stores the pending error in a dedicated net_context.sock_error field and converts every producer and consumer to sock_set_error()/sock_get_error(), leaving user_data untouched. As a side effect it also stops getsockopt(SO_ERROR) \u2014 which is evaluated unconditionally \u2014 from returning the kernel address held in user_data to a userspace application."
}
],
"id": "CVE-2026-18417",
"lastModified": "2026-09-29T00:17:04.207",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "ADJACENT_NETWORK",
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"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
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"impactScore": 3.6,
"source": "vulnerabilities@zephyrproject.org",
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}
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"published": "2026-09-29T00:17:04.207",
"references": [
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ef370a57d07637aaee8cec7b0bcebf4002ac8f54"
},
{
"source": "vulnerabilities@zephyrproject.org",
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-p8r8-8mw8-3wf9"
}
],
"sourceIdentifier": "vulnerabilities@zephyrproject.org",
"vulnStatus": "Received",
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"description": [
{
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"value": "CWE-843"
}
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"source": "vulnerabilities@zephyrproject.org",
"type": "Secondary"
}
]
}
}
}
}
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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
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- Confirmed: The vulnerability has been validated from an analyst's perspective.
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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- 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.
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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
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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.
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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.
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