CVE-2026-89546
In the Linux kernel, the following vulnerability has been resolved:
SUNRPC: close backchannel before destroying callback service
A backchannel receive can complete a request while the NFS callback service is being torn down. xprt_complete_bc_request() removes the request from bc_pa_list, drops bc_alloc_count, marks the request in use, and then asks xprt_enqueue_bc_request() to hand it to the callback service.
If teardown has already cleared xprt->bc_serv, xprt_enqueue_bc_request() currently returns without enqueueing or freeing the committed request. The xprt_get() taken on entry is leaked as well.
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If the producer wins the race before bc_serv is cleared, it can also enqueue onto sv_cb_list after nfs_callback_down() has stopped the callback threads, leaving the request linked to a svc_serv that is about to be freed.
Close the producer side before callback threads are stopped. Add xprt_svc_shutdown_bc() to clear xprt->bc_serv under bc_pa_lock, and call it on callback shutdown and callback-start failure before stopping the service threads. Requests that lose the NULL transition in xprt_enqueue_bc_request() are released through the normal backchannel free path after balancing bc_slot_count. Finally, drain any remaining sv_cb_list requests after the callback threads have stopped and before svc_destroy() frees the service.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 9.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.55%
- Percentil entre todas las CVEs puntuadas: 44
- 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
T1190Exploit Public-Facing Applicationinitial access60 %
Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.
🛡️ 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.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-89546",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 9.8,
"attackVector": "NETWORK",
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "NONE",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 3.9
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
"lessThan": "6debde9e3e6ae21dcca75837b4247b13ca4ea2b8",
"versionType": "git"
},
{
"status": "affected",
"version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
"lessThan": "3674f780f47d2906b5a0f7199b66973067bdfeca",
"versionType": "git"
}
],
"programFiles": [
"fs/nfs/callback.c",
"include/linux/sunrpc/bc_xprt.h",
"net/sunrpc/backchannel_rqst.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.19"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.19",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/nfs/callback.c",
"include/linux/sunrpc/bc_xprt.h",
"net/sunrpc/backchannel_rqst.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-11T20:19:37.960",
"references": [
{
"url": "https://git.kernel.org/stable/c/3674f780f47d2906b5a0f7199b66973067bdfeca",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/6debde9e3e6ae21dcca75837b4247b13ca4ea2b8",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: close backchannel before destroying callback service\n\nA backchannel receive can complete a request while the NFS callback\nservice is being torn down. xprt_complete_bc_request() removes the\nrequest from bc_pa_list, drops bc_alloc_count, marks the request in use,\nand then asks xprt_enqueue_bc_request() to hand it to the callback\nservice.\n\nIf teardown has already cleared xprt->bc_serv, xprt_enqueue_bc_request()\ncurrently returns without enqueueing or freeing the committed request.\nThe xprt_get() taken on entry is leaked as well. If the producer wins\nthe race before bc_serv is cleared, it can also enqueue onto sv_cb_list\nafter nfs_callback_down() has stopped the callback threads, leaving the\nrequest linked to a svc_serv that is about to be freed.\n\nClose the producer side before callback threads are stopped. Add\nxprt_svc_shutdown_bc() to clear xprt->bc_serv under bc_pa_lock, and call\nit on callback shutdown and callback-start failure before stopping the\nservice threads. Requests that lose the NULL transition in\nxprt_enqueue_bc_request() are released through the normal backchannel\nfree path after balancing bc_slot_count. Finally, drain any remaining\nsv_cb_list requests after the callback threads have stopped and before\nsvc_destroy() frees the service."
}
],
"lastModified": "2026-09-13T07:17:16.950",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}