VulnerabilityPublished 11 Sep 2026Updated 21 Oct 2026

CVE-2026-89685: Linux kernel · nfsd: fix clock domain mismatch in clients_still_reclaiming()

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in f9cec313efb2fd18d962aad738a4892bce806016 : patch Linux kernel soon.

Data as of 26 Oct 2026, 19:50 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS

0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in f9cec313efb2fd18d962aad738a4892bce806016, e92e80c5b043108029bc729b30d12c37158fb9cb, 9843649196221152b6e5d138a3ce859bdaae1d96 +2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf, < f9cec313efb2fd18d962aad738a4892bce806016	Fixed in f9cec313efb2fd18d962aad738a4892bce806016
LinuxLinux	Affected ≥ 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf, < e92e80c5b043108029bc729b30d12c37158fb9cb	Fixed in e92e80c5b043108029bc729b30d12c37158fb9cb
LinuxLinux	Affected ≥ 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf, < 9843649196221152b6e5d138a3ce859bdaae1d96	Fixed in 9843649196221152b6e5d138a3ce859bdaae1d96
LinuxLinux	Affected ≥ 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf, < 09ea3eb9a518565f5bca386e81b993ed8825f5e8	Fixed in 09ea3eb9a518565f5bca386e81b993ed8825f5e8
LinuxLinux	Affected ≥ 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf, < 04c3e4456fe76e8d7c94171009df3165c3262c51	Fixed in 04c3e4456fe76e8d7c94171009df3165c3262c51
LinuxLinux	Affected =5.6	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel versions identified by the fixed commit hashes. Users should update to a Linux kernel version that includes these fixes to remediate the vulnerability. No additional mitigation is required beyond applying the official patch.

Description

CVE-2026-89685 is a vulnerability in the Linux kernel's NFS server (nfsd) where a clock domain mismatch in the clients_still_reclaiming() function allows clients to indefinitely hold the server in grace by sending CLAIM_PREVIOUS OPEN requests. This blocks non-reclaim operations for other clients. The issue arises because the deadline is computed using CLOCK_REALTIME but compared against CLOCK_BOOTTIME, making the comparison always false. A fix has been implemented by adding a boot_time_bt value using CLOCK_BOOTTIME for deadline computation.

Impact

The vulnerability allows a client to indefinitely block the NFS server from processing non-reclaim operations for all other clients by exploiting the clock mismatch. This results in a denial of service condition affecting availability. There is no impact on confidentiality or integrity. The CVSS v3.1 score is 7.5 (high severity) with network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 19:50 UTC

Technical details

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