CVE-2026-72315
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix busy dentry warning on unmount after DIO
Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed the issue in cifs where deferred close of a file led to a dentry reference count not being released in umount, by flushing deferredclose_wq in cifs_kill_sb() to solve it.
However, the cifs DIO path suffers from the same busy-dentry problem caused by a delayed dentry reference-count release:
[dio] [cifsd] [close + umount] netfs_unbuffered_write_iter_locked ... cifs_demultiplex_thread netfs_unbuffered_write cifs_issue_write netfs_wait_for_in_progress_stream [1] ... netfs_write_subrequest_terminated netfs_subreq_clear_in_progress netfs_wake_collector // wake [1] netfs_put_subrequest netfs_put_request queue_work(system_dfl_wq, xxx) [2] // dio write return cifs_close _cifsFileInfo_put // cfile->count 2->1 --cfile->count [3]
Leer descripción completaMostrar menos
// umount cifs_kill_sb kill_anon_super // warning triggered! shrink_dcache_for_umount [4] [system_dfl_wq] [5] netfs_free_request ... _cifsFileInfo_put // cfile->count 1->0 --cfile->count queue_work(fileinfo_put_wq, xxx)
[fileinfo_put_wq] [6] cifsFileInfo_put_work cifsFileInfo_put_final dput
If the umount path is triggered before [5], it results warning: BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1) [unmount of cifs cifs]
The existing per-inode ictx->io_count wait in cifs_evict_inode() does not help: it lives in the inode eviction path, which runs after shrink_dcache_for_umount() has already warned about the busy dentries.
Fix it by adding a per-superblock outstanding-rreq counter that is incremented in cifs_init_request() and decremented in cifs_free_request(). In cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach 0 - which guarantees that all cleanup_work for this sb have run and thus all relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq. Then drain the workqueue so the dentry refs are dropped.
This is a targeted wait, not a flush of the system-wide system_dfl_wq.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.18%
- Percentil entre todas las CVEs puntuadas: 6
- Fecha de la puntuación: 6/10/2026
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
T1068Exploitation for Privilege Escalationprivilege escalation75 % - Impacto principal
T1499.004Application or System Exploitationimpact60 %
Vulnerabilidad de escalada de privilegios local (AV:L, PR:L) en kernel Linux que permite a usuario con privilegios locales obtener acceso de lectura/escritura/ejecución completos (C:H, I:H, A:H); causa negación de servicio por fuga de referencias en dentry durante desmontaje.
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.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-72315",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.8,
"attackVector": "LOCAL",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 1.8
}
]
},
"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": "0e4b8faaaebe3137bec5723ef2b3cb0437fb38fd",
"lessThan": "f7748b551010c021d92f0125e37f32ac0c376d8a",
"versionType": "git"
},
{
"status": "affected",
"version": "f655467a9973f964b267871e5fef533ad5014494",
"lessThan": "9fc87899276af941ecf3045798887db7deb85605",
"versionType": "git"
},
{
"status": "affected",
"version": "340cea84f691c5206561bb2e0147158fe02070be",
"lessThan": "f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214",
"versionType": "git"
},
{
"status": "affected",
"version": "340cea84f691c5206561bb2e0147158fe02070be",
"lessThan": "75f5c412fa867efa0bf9b646bffe0d912109e84a",
"versionType": "git"
},
{
"status": "affected",
"version": "708c276f516d27beaded7f372ac8111cee43926c",
"versionType": "git"
},
{
"status": "affected",
"version": "0629a1a187e424373364d681b42b101894bdb548",
"versionType": "git"
},
{
"status": "affected",
"version": "30afc6ea72cc6cf7c8d579e79b64232801c38d08",
"versionType": "git"
},
{
"status": "affected",
"version": "6.12.78",
"lessThan": "6.12.112",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.18.20",
"lessThan": "6.18.54",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.1.167",
"lessThan": "6.2",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.130",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.19.10",
"lessThan": "6.20",
"versionType": "semver"
}
],
"programFiles": [
"fs/smb/client/cifs_fs_sb.h",
"fs/smb/client/cifsfs.c",
"fs/smb/client/connect.c",
"fs/smb/client/file.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.54",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/smb/client/cifs_fs_sb.h",
"fs/smb/client/cifsfs.c",
"fs/smb/client/connect.c",
"fs/smb/client/file.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T06:22:04.367",
"references": [
{
"url": "https://git.kernel.org/stable/c/75f5c412fa867efa0bf9b646bffe0d912109e84a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9fc87899276af941ecf3045798887db7deb85605",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f7748b551010c021d92f0125e37f32ac0c376d8a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix busy dentry warning on unmount after DIO\n\nCommit c68337442f03 (\"cifs: Fix busy dentry used after unmounting\") fixed\nthe issue in cifs where deferred close of a file led to a dentry reference\ncount not being released in umount, by flushing deferredclose_wq in\ncifs_kill_sb() to solve it.\n\nHowever, the cifs DIO path suffers from the same busy-dentry problem caused\nby a delayed dentry reference-count release:\n\n\t[dio]\t\t\t[cifsd]\t\t\t[close + umount]\nnetfs_unbuffered_write_iter_locked\n...\n\t\t\t\tcifs_demultiplex_thread\n netfs_unbuffered_write\n cifs_issue_write\n netfs_wait_for_in_progress_stream [1]\n\t\t\t\t...\n\t\t\t\t netfs_write_subrequest_terminated\n\t\t\t\t netfs_subreq_clear_in_progress\n\t\t\t\t netfs_wake_collector // wake [1]\n\t\t\t\t netfs_put_subrequest\n netfs_put_request\n queue_work(system_dfl_wq, xxx) [2]\n // dio write return\t\t\t\t\tcifs_close\n\t\t\t\t\t\t\t _cifsFileInfo_put\n\t\t\t\t\t\t\t // cfile->count 2->1\n\t\t\t\t\t\t\t --cfile->count [3]\n\n\t\t\t\t\t\t\t// umount\n\t\t\t\t\t\t\tcifs_kill_sb\n\t\t\t\t\t\t\t kill_anon_super\n\t\t\t\t\t\t\t // warning triggered!\n\t\t\t\t\t\t\t shrink_dcache_for_umount [4]\n[system_dfl_wq] [5]\nnetfs_free_request\n ...\n _cifsFileInfo_put\n // cfile->count 1->0\n --cfile->count\n queue_work(fileinfo_put_wq, xxx)\n\n[fileinfo_put_wq] [6]\ncifsFileInfo_put_work\n cifsFileInfo_put_final\n dput\n\nIf the umount path is triggered before [5], it results warning:\nBUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1)\n[unmount of cifs cifs]\n\nThe existing per-inode ictx->io_count wait in cifs_evict_inode() does not\nhelp: it lives in the inode eviction path, which runs after\nshrink_dcache_for_umount() has already warned about the busy dentries.\n\nFix it by adding a per-superblock outstanding-rreq counter that is\nincremented in cifs_init_request() and decremented in cifs_free_request().\nIn cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach\n0 - which guarantees that all cleanup_work for this sb have run and thus\nall relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq.\nThen drain the workqueue so the dentry refs are dropped.\n\nThis is a targeted wait, not a flush of the system-wide system_dfl_wq."
}
],
"lastModified": "2026-10-03T11:17:37.153",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}