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CVE-2026-31446— ext4: fix use-after-free in update_super_work when racing with umount

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于update_super_work函数在卸载时存在释放后重用，可能导致访问已释放的kernfs_node。

CVSS 7.8 · High EPSS 0.19% · P8

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 21

VendorProduct Version RangeStatus
Linux Linux 52c3a04f9ec2a16a4204d6274db338cb8d5b2d74< c8fe17a1b308c3d8c703ebfb049b325f844342c3 affected
b98535d091795a79336f520b0708457aacf55c67< c4d829737329f2290dd41e290b7d75effdb2a7ff affected
b98535d091795a79336f520b0708457aacf55c67< 9449f99ba04f5dd1c8423ad8a90b3651d7240d1d affected
b98535d091795a79336f520b0708457aacf55c67< 034053378dd81837fd6c7a43b37ee2e58d4f0b4e affected
b98535d091795a79336f520b0708457aacf55c67< c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe affected
b98535d091795a79336f520b0708457aacf55c67< 08b10e6f37fc533a759e9833af0692242e8b3f93 affected
b98535d091795a79336f520b0708457aacf55c67< d15e4b0a418537aafa56b2cb80d44add83e83697 affected
585ef03c9e79672781f954daae730dfe24bf3a46 affected
… +13 more rows
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I. Basic Information for CVE-2026-31446

Vulnerability Information
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Vulnerability Title
ext4: fix use-after-free in update_super_work when racing with umount
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于update_super_work函数在卸载时存在释放后重用，可能导致访问已释放的kernfs_node。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 52c3a04f9ec2a16a4204d6274db338cb8d5b2d74 ~ c8fe17a1b308c3d8c703ebfb049b325f844342c3 -
Linux Linux 5.18 -

II. Public POCs for CVE-2026-31446

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III. Intelligence Information for CVE-2026-31446

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Same Patch Batch · Linux · 2026-04-22 · 100 CVEs total

CVE-2026-31463 9.8 CRITICAL iomap: fix invalid folio access when i_blkbits differs from I/O granularity
CVE-2026-31436 9.8 CRITICAL dmaengine: idxd: fix possible wrong descriptor completion in llist_abort_desc()
CVE-2026-31444 9.8 CRITICAL ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
CVE-2026-31478 9.8 CRITICAL ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()
CVE-2026-31501 9.8 CRITICAL net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path
CVE-2026-31448 9.4 CRITICAL ext4: avoid infinite loops caused by residual data
CVE-2026-31432 8.8 HIGH ksmbd: fix OOB write in QUERY_INFO for compound requests
CVE-2026-31433 8.8 HIGH ksmbd: fix potencial OOB in get_file_all_info() for compound requests
CVE-2026-31435 8.8 HIGH netfs: Fix read abandonment during retry
CVE-2026-31450 8.8 HIGH ext4: publish jinode after initialization
CVE-2026-31476 8.2 HIGH ksmbd: do not expire session on binding failure
CVE-2026-31464 8.1 HIGH scsi: ibmvfc: Fix OOB access in ibmvfc_discover_targets_done()
CVE-2026-31513 8.1 HIGH Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req
CVE-2026-31490 7.8 HIGH drm/xe/pf: Fix use-after-free in migration restore
CVE-2026-31479 7.8 HIGH drm/xe: always keep track of remap prev/next
CVE-2026-31494 7.8 HIGH net: macb: use the current queue number for stats
CVE-2026-31502 7.8 HIGH team: fix header_ops type confusion with non-Ethernet ports
CVE-2026-31449 7.8 HIGH ext4: validate p_idx bounds in ext4_ext_correct_indexes
CVE-2026-31504 7.8 HIGH net: fix fanout UAF in packet_release() via NETDEV_UP race
CVE-2026-31505 7.8 HIGH iavf: fix out-of-bounds writes in iavf_get_ethtool_stats()

Showing top 20 of 100 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31446

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