VulnerabilityPublished 11 Sep 2026Updated 5 Oct 2026

CVE-2026-89666: Linux kernel · nfsd: reject out-of-range nseconds in NFSv3 SETATTR and create ops

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-89666

Not known to be exploited.

Data as of 26 Oct 2026, 15:59 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 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.

ghsa-55g6-jf39-8gg4

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that validates client-supplied atime and mtime nanosecond values in the NFSv3 server handlers, rejecting out-of-range values before any changes are made. Systems should apply the official Linux kernel updates that include this validation to prevent metadata corruption. No additional mitigation is required as the patch prevents the issue at the protocol handling stage.

Description

A vulnerability in the Linux kernel's NFSv3 server implementation allows a client to send out-of-range nanosecond values in file timestamps (atime or mtime) during SETATTR and create operations. This causes corruption of on-disk metadata timestamps in filesystems like ext4 and XFS, leading to incorrect stored time values. The issue arises because the kernel did not properly validate the nanosecond field, allowing invalid values to be stored. The vulnerability has been resolved by validating client-supplied timestamps early in the request handling to reject invalid values before any changes occur.

Impact

The vulnerability leads to corruption of on-disk metadata timestamps (atime and mtime) in affected filesystems like ext4 and XFS when invalid nanosecond values are accepted. This can cause incorrect file time information to be stored and reported, potentially impacting file integrity and time-based operations. There is no indication of remote code execution or privilege escalation. The issue affects NFSv3 clients sending malformed timestamp data to the server.

Summary

The Linux kernel's NFSv3 server (nfsd) previously accepted client requests with atime or mtime nanosecond fields (tv_nsec) that were out of the valid range (tv_nsec must be less than NSEC_PER_SEC). While the value decodes as a valid uint32, it is not a valid timespec64, and the kernel did not clamp or reject it. This caused corruption of on-disk timestamps in filesystems such as ext4 and XFS, where the nanosecond value overflowed storage fields and clobbered the seconds portion, resulting in incorrect time and year values upon read-back. The fix involves validating these client-supplied timestamps in the proc handlers before any object creation or attribute setting, returning NFS3ERR_INVAL for invalid values, thus preventing metadata corruption and ensuring protocol correctness.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 02:43 UTC

Technical details

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