CVE-2026-31446ext4: fix use-after-free in update_super_work when racing with umount
Updated under an hour ago ()
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In the Linux kernel, the following vulnerability has been resolved: ext4: fix use-after-free in update_super_work when racing with umount Commit b98535d09179 ("ext4: fix bug_on in start_this_handle during umount filesystem") moved ext4_unregister_sysfs() before flushing s_sb_upd_work to prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups reads during unmount. However, this introduced a use-after-free because update_super_work calls ext4_notify_error_sysfs() -> sysfs_notify() which accesses the kobject's kernfs_node after it has been freed by kobject_del() in ext4_unregister_sysfs(): update_super_work ext4_put_super ----------------- -------------- ext4_unregister_sysfs(sb) kobject_del(&sbi->s_kobj) __kobject_del() sysfs_remove_dir() kobj->sd = NULL sysfs_put(sd) kernfs_put() // RCU free ext4_notify_error_sysfs(sbi) sysfs_notify(&sbi->s_kobj) kn = kobj->sd // stale pointer kernfs_get(kn) // UAF on freed kernfs_node ext4_journal_destroy() flush_work(&sbi->s_sb_upd_work) Instead of reordering the teardown sequence, fix this by making ext4_notify_error_sysfs() detect that sysfs has already been torn down by checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call in that case. A dedicated mutex (s_error_notify_mutex) serializes ext4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs() to prevent TOCTOU races where the kobject could be deleted between the state_in_sysfs check and the sysfs_notify() call.
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 52c3a04f9ec2a16a4204d6274db338cb8d5b2d74 before c8fe17a1b308c3d8c703ebfb049b325f844342c3; from b98535d091795a79336f520b0708457aacf55c67 before c4d829737329f2290dd41e290b7d75effdb2a7ff; from b98535d091795a79336f520b0708457aacf55c67 before 9449f99ba04f5dd1c8423ad8a90b3651d7240d1d; from b98535d091795a79336f520b0708457aacf55c67 before 034053378dd81837fd6c7a43b37ee2e58d4f0b4e; from b98535d091795a79336f520b0708457aacf55c67 before c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe; from b98535d091795a79336f520b0708457aacf55c67 before 08b10e6f37fc533a759e9833af0692242e8b3f93; from b98535d091795a79336f520b0708457aacf55c67 before d15e4b0a418537aafa56b2cb80d44add83e83697; 585ef03c9e79672781f954daae730dfe24bf3a46; and 4 more ranges | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 5.10.114 before 5.11; from 5.15.38 before 5.15.203; from 5.17.6 before 5.18; from 5.18.1 before 6.1.168; from 6.2 before 6.6.131; from 6.7 before 6.12.80; from 6.13 before 6.18.21; from 6.19 before 6.19.11; and 11 more ranges | NVD |
References
- https://git.kernel.org/stable/c/c8fe17a1b308c3d8c703ebfb049b325f844342c3patch
- https://git.kernel.org/stable/c/c4d829737329f2290dd41e290b7d75effdb2a7ffpatch
- https://git.kernel.org/stable/c/9449f99ba04f5dd1c8423ad8a90b3651d7240d1dpatch
- https://git.kernel.org/stable/c/034053378dd81837fd6c7a43b37ee2e58d4f0b4epatch
- https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffepatch
- https://git.kernel.org/stable/c/08b10e6f37fc533a759e9833af0692242e8b3f93patch
- https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.