CVE-2026-64378 (GCVE-0-2026-64378)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-08-17 04:54
VLAI
Title
writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()
Summary
In the Linux kernel, the following vulnerability has been resolved: writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs() When a container exits, the following BUG_ON() is occasionally triggered: ================================================================== VFS: Busy inodes after unmount of sdb (ext4) ------------[ cut here ]------------ kernel BUG at fs/super.c:695! CPU: 3 PID: 6 Comm: containerd-shim Tainted: G OE K 6.6 #1 pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : generic_shutdown_super+0xf0/0x100 lr : generic_shutdown_super+0xf0/0x100 Call trace: generic_shutdown_super+0xf0/0x100 kill_block_super+0x20/0x48 ext4_kill_sb+0x28/0x60 deactivate_locked_super+0x54/0x130 deactivate_super+0x84/0xa0 cleanup_mnt+0xa4/0x140 __cleanup_mnt+0x18/0x28 task_work_run+0x78/0xe0 do_notify_resume+0x204/0x240 ================================================================== The root cause is a race between cgroup_writeback_umount() and inode_switch_wbs()/cleanup_offline_cgwb(). There is a window between inode_prepare_wbs_switch() returning true and the subsequent wb_queue_isw() call. Following is the process that triggers the issue: CPU A (umount) | CPU B (writeback) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ inode_switch_wbs/cleanup_offline_cgwb atomic_inc(&isw_nr_in_flight) inode_prepare_wbs_switch -> passes SB_ACTIVE check __iget(inode) generic_shutdown_super sb->s_flags &= ~SB_ACTIVE cgroup_writeback_umount(sb) smp_mb() atomic_read(&isw_nr_in_flight) rcu_barrier() -> no pending RCU callbacks flush_workqueue(isw_wq) -> nothing queued, returns evict_inodes(sb) -> Inode skipped as isw still holds a ref. sop->put_super(sb) /* destroys percpu counters */ -> VFS: Busy inodes after unmount! wb_queue_isw() queue_work(isw_wq, ...) /* later in work function */ inode_switch_wbs_work_fn process_inode_switch_wbs iput() -> evict percpu_counter_dec() // UAF! Fix this by extending the RCU read-side critical section in inode_switch_wbs() and cleanup_offline_cgwb() to cover from inode_prepare_wbs_switch() through wb_queue_isw(). Since there is no sleep in this window, rcu_read_lock() can be used. Then add a synchronize_rcu() in cgroup_writeback_umount() before the existing rcu_barrier(), so that all in-flight switchers that have passed the SB_ACTIVE check have completed queue_work() before flush_workqueue() is called. The existing rcu_barrier() is intentionally retained so this fix can be backported unchanged to stable kernels (5.10.y, 6.6.y, ...) that still queue switches via queue_rcu_work(). It is a no-op on current mainline (since commit e1b849cfa6b6 ("writeback: Avoid contention on wb->list_lock when switching inodes")) and is removed in a follow-up patch.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < 087d5b8b501c570f84bf655164e6698c3ce146e0 (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < 3c9c9648f77e4d14e50676bc51c2174ba9c8d361 (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < 5c3265f3252b2ee50707adaaa3f9bd0df3df72de (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < c923cc3cb5cd8945ceaf08252754110643446593 (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < 685fc15a410885b6d4dee64de0dce721b9428b12 (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < 53eeaf4d63068dbc7708b0c7adb20151c812feca (git)
Affected: a1a0e23e49037c23ea84bc8cc146a03584d13577 , < cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d (git)
Affected: c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339 (git)
Affected: 4.4.5 , < 4.5 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 4.5
Unaffected: 0 , < 4.5 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fs-writeback.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "087d5b8b501c570f84bf655164e6698c3ce146e0",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "3c9c9648f77e4d14e50676bc51c2174ba9c8d361",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "5c3265f3252b2ee50707adaaa3f9bd0df3df72de",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "c923cc3cb5cd8945ceaf08252754110643446593",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "685fc15a410885b6d4dee64de0dce721b9428b12",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "53eeaf4d63068dbc7708b0c7adb20151c812feca",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "lessThan": "cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d",
              "status": "affected",
              "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339",
              "versionType": "git"
            },
            {
              "lessThan": "4.5",
              "status": "affected",
              "version": "4.4.5",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/fs-writeback.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.5"
            },
            {
              "lessThan": "4.5",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.261",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.145",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.96",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.261",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.178",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.145",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.96",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.39",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.4",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "4.5",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "4.4.5",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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(\u0026isw_nr_in_flight)\n                                  inode_prepare_wbs_switch\n                                   -\u003e passes SB_ACTIVE check\n                                   __iget(inode)\n generic_shutdown_super\n  sb-\u003es_flags \u0026= ~SB_ACTIVE\n  cgroup_writeback_umount(sb)\n   smp_mb()\n   atomic_read(\u0026isw_nr_in_flight)\n   rcu_barrier()\n    -\u003e no pending RCU callbacks\n   flush_workqueue(isw_wq)\n    -\u003e nothing queued, returns\n  evict_inodes(sb)\n   -\u003e Inode skipped as isw still holds a ref.\n  sop-\u003eput_super(sb)\n   /* destroys percpu counters */\n  -\u003e 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() -\u003e 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-\u003elist_lock when switching inodes\")) and is removed in a follow-up\npatch."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:54:29.511Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64378",
    "datePublished": "2026-07-25T08:50:29.006Z",
    "dateReserved": "2026-07-19T15:36:31.784Z",
    "dateUpdated": "2026-08-17T04:54:29.511Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-64378",
      "date": "2026-09-20",
      "epss": "0.001",
      "percentile": "0.00954"
    },
    "microsoft_vex": {
      "current_release_date": "2026-07-27T14:44:11.000Z",
      "cve": "CVE-2026-64378",
      "id": "msrc_CVE-2026-64378",
      "initial_release_date": "2026-07-26T01:01:52.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64378.json",
      "version": "2"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/fs-writeback.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "087d5b8b501c570f84bf655164e6698c3ce146e0",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "3c9c9648f77e4d14e50676bc51c2174ba9c8d361",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "5c3265f3252b2ee50707adaaa3f9bd0df3df72de",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "c923cc3cb5cd8945ceaf08252754110643446593",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "685fc15a410885b6d4dee64de0dce721b9428b12",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "53eeaf4d63068dbc7708b0c7adb20151c812feca",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d",
                    "status": "affected",
                    "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577",
                    "versionType": "git"
                  },
                  {
                    "status": "affected",
                    "version": "c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "4.5",
                    "status": "affected",
                    "version": "4.4.5",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "fs/fs-writeback.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "4.5"
                  },
                  {
                    "lessThan": "4.5",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "5.10.*",
                    "status": "unaffected",
                    "version": "5.10.261",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.1.*",
                    "status": "unaffected",
                    "version": "6.1.178",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.6.*",
                    "status": "unaffected",
                    "version": "6.6.145",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.12.*",
                    "status": "unaffected",
                    "version": "6.12.96",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.18.*",
                    "status": "unaffected",
                    "version": "6.18.39",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.1.*",
                    "status": "unaffected",
                    "version": "7.1.4",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.2",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "DB6331F3-ABBB-4697-A9F2-E74650DD2EFF",
                    "versionEndExcluding": "4.5",
                    "versionStartIncluding": "4.4.5",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "C58D417F-A474-4EDA-8612-02CCC730A9C9",
                    "versionEndExcluding": "5.10.261",
                    "versionStartIncluding": "4.5.1",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "A3F98F31-C139-4297-934F-35550253E78F",
                    "versionEndExcluding": "6.1.178",
                    "versionStartIncluding": "5.11",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "7046B092-F810-4440-ACE6-60218518EECE",
                    "versionEndExcluding": "6.6.145",
                    "versionStartIncluding": "6.2",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "38A8100E-2B1A-462F-AEE9-8901B870FEF2",
                    "versionEndExcluding": "6.12.96",
                    "versionStartIncluding": "6.7",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "914AE4BC-3D59-4C5A-9DB5-9CE327B429F7",
                    "versionEndExcluding": "6.18.39",
                    "versionStartIncluding": "6.13",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "6228DDD6-4557-4AA3-9F43-AB995D471E42",
                    "versionEndExcluding": "7.1.4",
                    "versionStartIncluding": "6.19",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:4.5:-:*:*:*:*:*:*",
                    "matchCriteriaId": "28316352-6847-4D33-8E69-F3C933F42A04",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:4.5:rc7:*:*:*:*:*:*",
                    "matchCriteriaId": "80AD3822-AE03-412E-8E14-0DAD0BDCA028",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "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(\u0026isw_nr_in_flight)\n                                  inode_prepare_wbs_switch\n                                   -\u003e passes SB_ACTIVE check\n                                   __iget(inode)\n generic_shutdown_super\n  sb-\u003es_flags \u0026= ~SB_ACTIVE\n  cgroup_writeback_umount(sb)\n   smp_mb()\n   atomic_read(\u0026isw_nr_in_flight)\n   rcu_barrier()\n    -\u003e no pending RCU callbacks\n   flush_workqueue(isw_wq)\n    -\u003e nothing queued, returns\n  evict_inodes(sb)\n   -\u003e Inode skipped as isw still holds a ref.\n  sop-\u003eput_super(sb)\n   /* destroys percpu counters */\n  -\u003e 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() -\u003e 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-\u003elist_lock when switching inodes\")) and is removed in a follow-up\npatch."
          }
        ],
        "id": "CVE-2026-64378",
        "lastModified": "2026-09-08T15:23:22.650",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-25T10:17:20.940",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/087d5b8b501c570f84bf655164e6698c3ce146e0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/3c9c9648f77e4d14e50676bc51c2174ba9c8d361"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/53eeaf4d63068dbc7708b0c7adb20151c812feca"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/5c3265f3252b2ee50707adaaa3f9bd0df3df72de"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/685fc15a410885b6d4dee64de0dce721b9428b12"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/c923cc3cb5cd8945ceaf08252754110643446593"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-362"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-07-27T07:27:00+00:00",
      "cve": "CVE-2026-64378",
      "id": "CVE-2026-64378",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "28",
      "product_status:under_investigation": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64378.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-18T00:41:03Z",
      "cve": "CVE-2026-64378",
      "id": "CVE-2026-64378",
      "initial_release_date": "2026-07-25T16:00:36Z",
      "product_status:known_affected": "729",
      "product_status:known_not_affected": "4",
      "product_status:recommended": "111",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64378",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64378.json",
      "version": "11"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • 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.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.