VulnerabilityPublished 18 Apr 2025Updated 7 Nov 2025

CVE-2025-39688: Linux kernel · nfsd: allow SC_STATUS_FREEABLE when searching via nfs4_lookup_stateid()

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 4 Nov 2026, 18:38 UTC

CVSS 3.1 base score

5.5Medium

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

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
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: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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 18 Apr 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 4 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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-53x5-v4j3-g5xm

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel by modifying nfs4_lookup_stateid() to allow the SC_STATUS_FREEABLE flag and adjusting delegation return handling. Users should apply the updated kernel version containing this fix. No additional mitigation actions are indicated.

Description

CVE-2025-39688 is a vulnerability in the Linux kernel's NFS server (nfsd) related to stateid lookup during delegation revocation. The issue involves the nfs4_lookup_stateid() function not allowing the SC_STATUS_FREEABLE flag when searching for stateids, causing revoked delegations to be improperly handled. This results in unexpected error codes when clients attempt to use revoked delegation stateids after lease expiration.

Impact

This vulnerability causes the NFS server to return incorrect error codes when clients use revoked delegation stateids after lease expiration. While it does not affect confidentiality or integrity, it impacts availability by causing denial of service conditions (indicated by the CVSS vector's high availability impact). There is no evidence of exploitation in the wild or direct compromise of data.

Summary

The vulnerability in the Linux kernel's nfsd component concerns the handling of delegation stateids during lookup via nfs4_lookup_stateid(). When a delegation is revoked, it is initially marked with SC_STATUS_REVOKED or SC_STATUS_ADMIN_REVOKED and later marked with SC_STATUS_FREEABLE, indicating it is awaiting a FREE_STATEID call. However, the statusmask used in nfs4_lookup_stateid() did not include SC_STATUS_FREEABLE, causing revoked delegations to be almost never found and resulting in incorrect error responses (NFS4ERR_BAD_STATEID instead of NFS4ERR_DELEG_REVOKED). The fix adds SC_STATUS_FREEABLE to the allowed status flags and removes redundant handling in nfsd4_delegreturn().

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