Linux Kernel up to 6.19.10 mb_groups ext4_unregister_sysfs use after free

CVSS Meta Temp Score
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CTI Interest Score
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7.7$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.19.10. This affects the function ext4_unregister_sysfs of the file /proc/fs/ext4/xx/mb_groups. The manipulation leads to use after free. This vulnerability is uniquely identified as CVE-2026-31446. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.19.10. This issue affects the function ext4_unregister_sysfs of the file /proc/fs/ext4/xx/mb_groups. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-31446 since 03/09/2026. The exploitation is known to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/17/2026).

The vulnerability scanner Nessus provides a plugin with the ID 313522 (Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2026-1681)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.203, 6.1.168, 6.6.131, 6.12.80, 6.18.21 or 6.19.11 eliminates this vulnerability. Applying the patch c8fe17a1b308c3d8c703ebfb049b325f844342c3/c4d829737329f2290dd41e290b7d75effdb2a7ff/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d/034053378dd81837fd6c7a43b37ee2e58d4f0b4e/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe/08b10e6f37fc533a759e9833af0692242e8b3f93/d15e4b0a418537aafa56b2cb80d44add83e83697 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (313522) and CERT Bund (WID-SEC-2026-1252). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.7

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.8
CNA Vector (Linux): 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 313522
Nessus Name: Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2026-1681)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.15.203/6.1.168/6.6.131/6.12.80/6.18.21/6.19.11
Patch: c8fe17a1b308c3d8c703ebfb049b325f844342c3/c4d829737329f2290dd41e290b7d75effdb2a7ff/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d/034053378dd81837fd6c7a43b37ee2e58d4f0b4e/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe/08b10e6f37fc533a759e9833af0692242e8b3f93/d15e4b0a418537aafa56b2cb80d44add83e83697

Timelineinfo

03/09/2026 CVE reserved
04/22/2026 +43 days Advisory disclosed
04/22/2026 +0 days VulDB entry created
07/17/2026 +85 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-31446 (🔒)
GCVE (CVE): GCVE-0-2026-31446
GCVE (VulDB): GCVE-100-358877
CERT Bund: WID-SEC-2026-1252 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 04/22/2026 17:06
Updated: 07/17/2026 01:40
Changes: 04/22/2026 17:06 (59), 04/24/2026 02:52 (7), 05/10/2026 05:45 (2), 06/04/2026 22:01 (1), 07/14/2026 11:21 (1), 07/17/2026 01:40 (11)
Complete: 🔍
Cache ID: 216::103

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