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CVE-2026-89835— f2fs: avoid NULL checkpoint thread access in sysfs

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.

在 Linux 内核中，已修复了以下漏洞： f2fs：避免在 sysfs 中对 NULL 检查点线程的访问 即使在检查点合并线程未运行时， 仍可能被启用。只读挂载是其中一种情况：f2fs 在此时不会启动 ，但 仍可通过 sysfs 写入。 的写入路径会更新保存的 ioprio 值，并在启用 时调用 以设置检查点线程的优先级。若 为 NULL，则会对一个空的 task 指针进行解引用操作，导致潜在的空指针解引用崩溃。 修复方式为：在 的 sysfs 写入路径中增加对 的保护，确保在更新 ioprio 的过程中，检查点

AI Predicted 5.5 Difficulty: Moderate EPSS 0.21% · P10

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux e65920661708b7c0f3db45c9cd5d0095034ee37f< a6573f3ffc19542de9ebc1a2b1f930fd48ba538c affected
e65920661708b7c0f3db45c9cd5d0095034ee37f< aefcec3bebdeed2bff444378122300763325ba23 affected
e65920661708b7c0f3db45c9cd5d0095034ee37f< 8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b affected
e65920661708b7c0f3db45c9cd5d0095034ee37f< 5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f affected
5.12 affected
< 5.12 unaffected
6.12.110≤ 6.12.* unaffected
6.18.51≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-89835

Vulnerability Information
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Vulnerability Title
f2fs: avoid NULL checkpoint thread access in sysfs
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: avoid NULL checkpoint thread access in sysfs checkpoint_merge can be enabled even when no checkpoint merge thread is running. A read-only mount is one case: f2fs does not start f2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through sysfs. The ckpt_thread_ioprio store path updates the saved ioprio value and, when checkpoint_merge is enabled, calls set_task_ioprio() for the checkpoint thread. If cprc->f2fs_issue_ckpt is NULL, that dereferences a NULL task pointer. Protect ckpt_thread_ioprio sysfs writes with s_umount as well, so the checkpoint thread cannot disappear under the store path while updating its ioprio.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux e65920661708b7c0f3db45c9cd5d0095034ee37f ~ a6573f3ffc19542de9ebc1a2b1f930fd48ba538c -
Linux Linux 5.12 -

II. Public POCs for CVE-2026-89835

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III. Intelligence Information for CVE-2026-89835

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Other References for CVE-2026-89835 (4)

Same Patch Batch · Linux · 2026-09-16 · 276 CVEs total

CVE-2026-90048 9.8 CRITICAL fs/ntfs3: fix slab-out-of-bounds write in ni_create_attr_list()
CVE-2026-90012 9.8 CRITICAL spi: Fix DMA mapping ownership on partial map failure
CVE-2026-89970 9.8 CRITICAL nvmet-auth: Synchronize timeout work during SQ teardown
CVE-2026-89857 9.8 CRITICAL scsi: qla2xxx: Hold qpair lock when sending NVMe LS reject
CVE-2026-89969 9.8 CRITICAL nvmet-tcp: fix out-of-bounds write when receiving an over-long PDU
CVE-2026-89847 9.8 CRITICAL scsi: qla2xxx: Avoid double completion in async IOCB timeout
CVE-2026-89972 9.8 CRITICAL nvme: add missing SRCU grace period in error path
CVE-2026-89990 9.8 CRITICAL ceph: lock mutex in ceph_mds_check_access()
CVE-2026-90036 9.8 CRITICAL NFSD: Prevent client use-after-free during blocked-lock reaping
CVE-2026-90038 9.8 CRITICAL NFSD: Prevent client use-after-free during export state revocation
CVE-2026-90037 9.8 CRITICAL NFSD: Prevent client use-after-free during close_lru reaping
CVE-2026-89788 9.8 CRITICAL ksmbd: fix tree connection use-after-free in smb2_tree_connect()
CVE-2026-89783 9.8 CRITICAL xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full
CVE-2026-90042 9.8 CRITICAL ceph: properly decrypt filenames in vmalloc() buffers
CVE-2026-89778 9.8 CRITICAL isofs: fix out-of-bounds page array access on empty zisofs block
CVE-2026-89915 9.3 CRITICAL KVM: arm64: Remove VM-wide VNCR mapping counter
CVE-2026-90049 9.3 CRITICAL net: skbuff: don't skb_tx_error() the source skb in skb_zerocopy()
CVE-2026-89775 9.3 CRITICAL KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation
CVE-2026-89916 9.3 CRITICAL KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry
CVE-2026-89930 9.3 CRITICAL KVM: nVMX: Service local TLB flushes on failed nested VM-Enter

Showing top 20 of 276 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89835

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