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vuln-cve/data/2026/64xxx/CVE-2026-64378.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-64378",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2026-07-19T15:36:31.784Z",
"datePublished": "2026-07-25T08:50:29.006Z",
"dateUpdated": "2026-10-19T20:38:25.561Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-08-17T04:54:29.511Z"
},
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: fix race between cgroup_writeback_umount() and inode_switch_wbs()\n\nWhen a container exits, the following BUG_ON() is occasionally triggered:\n\n==================================================================\n VFS: Busy inodes after unmount of sdb (ext4)\n ------------[ cut here ]------------\n kernel BUG at fs/super.c:695!\n CPU: 3 PID: 6 Comm: containerd-shim Tainted: G OE K 6.6 #1\n pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)\n pc : generic_shutdown_super+0xf0/0x100\n lr : generic_shutdown_super+0xf0/0x100\n Call trace:\n generic_shutdown_super+0xf0/0x100\n kill_block_super+0x20/0x48\n ext4_kill_sb+0x28/0x60\n deactivate_locked_super+0x54/0x130\n deactivate_super+0x84/0xa0\n cleanup_mnt+0xa4/0x140\n __cleanup_mnt+0x18/0x28\n task_work_run+0x78/0xe0\n do_notify_resume+0x204/0x240\n==================================================================\n\nThe root cause is a race between cgroup_writeback_umount() and\ninode_switch_wbs()/cleanup_offline_cgwb(). There is a window between\ninode_prepare_wbs_switch() returning true and the subsequent\nwb_queue_isw() call. Following is the process that triggers the issue:\n\n CPU A (umount) | CPU B (writeback)\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n inode_switch_wbs/cleanup_offline_cgwb\n atomic_inc(&isw_nr_in_flight)\n inode_prepare_wbs_switch\n -> passes SB_ACTIVE check\n __iget(inode)\n generic_shutdown_super\n sb->s_flags &= ~SB_ACTIVE\n cgroup_writeback_umount(sb)\n smp_mb()\n atomic_read(&isw_nr_in_flight)\n rcu_barrier()\n -> no pending RCU callbacks\n flush_workqueue(isw_wq)\n -> nothing queued, returns\n evict_inodes(sb)\n -> Inode skipped as isw still holds a ref.\n sop->put_super(sb)\n /* destroys percpu counters */\n -> VFS: Busy inodes after unmount!\n wb_queue_isw()\n queue_work(isw_wq, ...)\n /* later in work function */\n inode_switch_wbs_work_fn\n process_inode_switch_wbs\n iput() -> evict\n percpu_counter_dec() // UAF!\n\nFix this by extending the RCU read-side critical section in\ninode_switch_wbs() and cleanup_offline_cgwb() to cover from\ninode_prepare_wbs_switch() through wb_queue_isw(). Since there is\nno sleep in this window, rcu_read_lock() can be used. Then add a\nsynchronize_rcu() in cgroup_writeback_umount() before the existing\nrcu_barrier(), so that all in-flight switchers that have passed the\nSB_ACTIVE check have completed queue_work() before flush_workqueue()\nis called.\n\nThe existing rcu_barrier() is intentionally retained so this fix can\nbe backported unchanged to stable kernels (5.10.y, 6.6.y, ...) that\nstill queue switches via queue_rcu_work(). It is a no-op on current\nmainline (since commit e1b849cfa6b6 (\"writeback: Avoid contention on\nwb->list_lock when switching inodes\")) and is removed in a follow-up\npatch."
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 7.8,
"baseSeverity": "HIGH"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The vulnerability is reached through local filesystem writes, cgroup teardown, and mount-namespace or filesystem unmount paths; no network protocol directly reaches the race.\nAC:L - An attacker can churn cgroup writeback switches while repeatedly triggering container or mount teardown, controlling both racing activities and amplifying the timing window.\nPR:L - A basic local or container user can dirty writable files and initiate its own cgroup or namespace teardown; lifecycle infrastructure can perform the privileged final unmount automatically.\nUI:N - The attacker can generate the writeback state and trigger teardown without requiring another user to perform an action.\nS:U - The resulting corruption affects the same host kernel security authority and does not inherently cross a VM or hardware isolation boundary.\nC:H - The delayed worker can access superblock-private state after it and its per-CPU counters have been freed, creating an exploitable use-after-free capable of exposing arbitrary kernel memory.\nI:H - The freed superblock and per-CPU counter pointers are subsequently dereferenced and modified, potentially providing attacker-influenced kernel writes and control-flow hijacking.\nA:H - The race demonstrably triggers the busy-inode BUG_ON, and configurations continuing past that check encounter a use-after-free capable of causing an oops or kernel panic."
}
]
}
],
"affected": [
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/fs-writeback.c"
],
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"status": "affected",
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{
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"lessThan": "cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d",
"status": "affected",
"versionType": "git"
},
{
"version": "c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339",
"status": "affected",
"versionType": "git"
},
{
"version": "4.4.5",
"lessThan": "4.5",
"status": "affected",
"versionType": "semver"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/fs-writeback.c"
],
"versions": [
{
"version": "4.5",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.5",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.10.261",
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.1.178",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.6.145",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.12.96",
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.18.39",
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.1.4",
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.5",
"versionEndExcluding": "5.10.261"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.5",
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},
{
"vulnerable": true,
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},
{
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.5",
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},
{
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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}
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}
],
"references": [
{
"url": "https://git.kernel.org/stable/c/087d5b8b501c570f84bf655164e6698c3ce146e0"
},
{
"url": "https://git.kernel.org/stable/c/3c9c9648f77e4d14e50676bc51c2174ba9c8d361"
},
{
"url": "https://git.kernel.org/stable/c/5c3265f3252b2ee50707adaaa3f9bd0df3df72de"
},
{
"url": "https://git.kernel.org/stable/c/c923cc3cb5cd8945ceaf08252754110643446593"
},
{
"url": "https://git.kernel.org/stable/c/685fc15a410885b6d4dee64de0dce721b9428b12"
},
{
"url": "https://git.kernel.org/stable/c/53eeaf4d63068dbc7708b0c7adb20151c812feca"
},
{
"url": "https://git.kernel.org/stable/c/cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d"
}
],
"title": "writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()",
"x_generator": {
"engine": "bippy-1.2.0"
}
},
"adp": [
{
"metrics": [
{
"other": {
"type": "ssvc",
"content": {
"id": "CVE-2026-64378",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"version": "2.0.3",
"timestamp": "2026-10-16T15:39:41.597767Z"
}
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"type": "CWE",
"cweId": "CWE-362",
"description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"
}
]
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP",
"dateUpdated": "2026-10-19T20:38:25.561Z"
}
}
]
}
}
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