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EUVD-2026-364739
European Vulnerability Database identifier assigned by ENISAReserved
2026-10-02 08:33
Assigner
ENISA
Alias of
a CVE record, shown under related vulnerabilities.
This identifier carries no description, severity or references of its own:
they belong to that CVE.
{
"assigner": "ENISA",
"date_reserved": "2026-10-02T08:33:49.842267+00:00",
"id": "EUVD-2026-364739"
}
CVE-2026-31446 (GCVE-0-2026-31446)
Vulnerability from cvelistv5 – Published: 2026-04-22 13:53 – Updated: 2026-09-08 08:47
VLAI
EPSS
VEX
Title
ext4: fix use-after-free in update_super_work when racing with umount
Summary
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.
Severity
7.8 (High)
Assigner
References
9 references
Impacted products
8 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
52c3a04f9ec2a16a4204d6274db338cb8d5b2d74 , < c8fe17a1b308c3d8c703ebfb049b325f844342c3
(git)
Affected: b98535d091795a79336f520b0708457aacf55c67 , < c4d829737329f2290dd41e290b7d75effdb2a7ff (git) Affected: b98535d091795a79336f520b0708457aacf55c67 , < 9449f99ba04f5dd1c8423ad8a90b3651d7240d1d (git) Affected: b98535d091795a79336f520b0708457aacf55c67 , < 034053378dd81837fd6c7a43b37ee2e58d4f0b4e (git) Affected: b98535d091795a79336f520b0708457aacf55c67 , < c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe (git) Affected: b98535d091795a79336f520b0708457aacf55c67 , < 08b10e6f37fc533a759e9833af0692242e8b3f93 (git) Affected: b98535d091795a79336f520b0708457aacf55c67 , < d15e4b0a418537aafa56b2cb80d44add83e83697 (git) Affected: 585ef03c9e79672781f954daae730dfe24bf3a46 (git) Affected: afe490e48d47df1b3f64012835c1bc2f075a8c8b (git) Affected: 5.15.38 , < 5.15.203 (semver) Affected: 5.10.114 , < 5.11 (semver) Affected: 5.17.6 , < 5.18 (semver) |
|
| Linux | Linux |
Affected:
5.18
Unaffected: 0 , < 5.18 (semver) Unaffected: 5.15.203 , ≤ 5.15.* (semver) Unaffected: 6.1.168 , ≤ 6.1.* (semver) Unaffected: 6.6.131 , ≤ 6.6.* (semver) Unaffected: 6.12.80 , ≤ 6.12.* (semver) Unaffected: 6.18.21 , ≤ 6.18.* (semver) Unaffected: 6.19.11 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix) |
|
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
|
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
|
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
|
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
|
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
|
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
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},
"references": [
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"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix use-after-free in update_super_work when racing with umount\n\nCommit b98535d09179 (\"ext4: fix bug_on in start_this_handle during umount\nfilesystem\") moved ext4_unregister_sysfs() before flushing s_sb_upd_work\nto prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups\nreads during unmount. However, this introduced a use-after-free because\nupdate_super_work calls ext4_notify_error_sysfs() -\u003e sysfs_notify() which\naccesses the kobject\u0027s kernfs_node after it has been freed by kobject_del()\nin ext4_unregister_sysfs():\n\n update_super_work ext4_put_super\n ----------------- --------------\n ext4_unregister_sysfs(sb)\n kobject_del(\u0026sbi-\u003es_kobj)\n __kobject_del()\n sysfs_remove_dir()\n kobj-\u003esd = NULL\n sysfs_put(sd)\n kernfs_put() // RCU free\n ext4_notify_error_sysfs(sbi)\n sysfs_notify(\u0026sbi-\u003es_kobj)\n kn = kobj-\u003esd // stale pointer\n kernfs_get(kn) // UAF on freed kernfs_node\n ext4_journal_destroy()\n flush_work(\u0026sbi-\u003es_sb_upd_work)\n\nInstead of reordering the teardown sequence, fix this by making\next4_notify_error_sysfs() detect that sysfs has already been torn down\nby checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call\nin that case. A dedicated mutex (s_error_notify_mutex) serializes\next4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs()\nto prevent TOCTOU races where the kobject could be deleted between the\nstate_in_sysfs check and the sysfs_notify() call."
}
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{
"lang": "en",
"value": "AV:L - The vulnerable ext4 paths are reached through local filesystem operations such as mounting/unmounting an ext4 image, reading ext4 procfs state, or writing ext4 sysfs controls; there is no direct network packet path.\nAC:L - The race is between queued ext4 superblock error work and teardown, and a crafted/ext4-error scenario can repeatedly drive the work while unmount/cleanup proceeds; under the required rule, this attacker-influenced race is Low complexity.\nPR:N - Directly initiating mount/umount or sysfs error injection requires CAP_SYS_ADMIN in the initial namespace, but a highest-severity reasonable scenario is an attacker-supplied crafted ext4 filesystem image mounted/unmounted by a victim or privileged automounter, requiring no attacker privilege.\nUI:R - Exploitation in the no-attacker-privilege scenario requires a victim or privileged system component to mount and later unmount/process the malicious ext4 filesystem image.\nS:U - The corruption occurs inside the kernel filesystem/sysfs/kernfs lifetime management for the same host kernel security authority; it is not a VM escape or cross-authority boundary break.\nC:H - The bug is a use-after-free of a kernfs_node reached through sysfs_notify after kobject deletion, and kernel UAFs are treated as capable of enabling high-impact information disclosure.\nI:H - The stale kernfs_node is refcounted and used after free, giving a memory-corruption primitive that is defensibly treated as potentially exploitable for kernel control-flow or data modification.\nA:H - At minimum the UAF can crash or oops the kernel during ext4 unmount/error-work processing, causing high availability impact."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:22:36.689Z",
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"url": "https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe"
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"url": "https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697"
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"title": "ext4: fix use-after-free in update_super_work when racing with umount",
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"cveId": "CVE-2026-31446",
"datePublished": "2026-04-22T13:53:42.751Z",
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"dateUpdated": "2026-09-08T08:47:09.923Z",
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Trend slope:
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(linear fit over daily sighting counts)
Show additional events:
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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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.
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