VulnerabilityPublished 16 Sep 2026Updated 21 Oct 2026

CVE-2026-89835: Linux kernel · f2fs: avoid NULL checkpoint thread access in sysfs

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in aefcec3bebdeed2bff444378122300763325ba23 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:07 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in aefcec3bebdeed2bff444378122300763325ba23, a6573f3ffc19542de9ebc1a2b1f930fd48ba538c, 22760e3e9cecbddc475edc91600787abf407a302 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ e65920661708b7c0f3db45c9cd5d0095034ee37f, < aefcec3bebdeed2bff444378122300763325ba23	Fixed in aefcec3bebdeed2bff444378122300763325ba23
LinuxLinux	Affected ≥ e65920661708b7c0f3db45c9cd5d0095034ee37f, < a6573f3ffc19542de9ebc1a2b1f930fd48ba538c	Fixed in a6573f3ffc19542de9ebc1a2b1f930fd48ba538c
LinuxLinux	Affected ≥ e65920661708b7c0f3db45c9cd5d0095034ee37f, < 22760e3e9cecbddc475edc91600787abf407a302	Fixed in 22760e3e9cecbddc475edc91600787abf407a302
LinuxLinux	Affected ≥ e65920661708b7c0f3db45c9cd5d0095034ee37f, < 8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b	Fixed in 8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b
LinuxLinux	Affected ≥ e65920661708b7c0f3db45c9cd5d0095034ee37f, < 5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f	Fixed in 5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f
LinuxLinux	Affected =5.12	Fixed in–

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.

References

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