CVE-2025-39688Network attack vector

Service degradation via unreleased revoked delegations

Published Apr 18, 2025 · Updated Aug 5, 2026

Resource exhaustion in Linux nfsd allows remote attackers to degrade NFS service by reusing revoked delegation stateids. nfs4_lookup_stateid() excludes SC_STATUS_FREEABLE from its allowed-status mask, so revoked delegations waiting for FREE_STATEID are not found or released. A client permitted by the export ACL can repeat ordinary NFSv4 operations to consume the global delegation limit and sustain service degradation without exposing or modifying data.

CVSS severity7.5
High
EPSS probability0.60%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Linux nfsd allows remote attackers to degrade NFS service by reusing revoked delegation stateids. nfs4_lookup_stateid() excludes SC_STATUS_FREEABLE from its allowed-status mask, so revoked delegations waiting for FREE_STATEID are not found or released. A client permitted by the export ACL can repeat ordinary NFSv4 operations to consume the global delegation limit and sustain service degradation without exposing or modifying data.

The record

CVE
CVE-2025-39688
Published
Apr 18, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 18, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.11.6 <6.12
  2. Affected versionversion=6.12
  3. Affected versionversion=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <52e209203c35a4fbff8af23cd3613efe5df40102
  4. Affected versionversion=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <5bcb44e650bc4ec7eac23df90c5e011a77fa2beb
  5. Affected versionversion=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <d1bc15b147d35b4cb7ca99a9a7d79d41ca342c13
  6. Affected versionversion=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <dc6f3295905d7185e71091870119a8c11c3808cc
  7. Affected versionversion=967faa26f313a62e7bebc55d5b8122eaee43b929

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.11.6 <6.12; version=6.12; version=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <52e209203c35a4fbff8af23cd3613efe5df40102; version=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <5bcb44e650bc4ec7eac23df90c5e011a77fa2beb; version=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <d1bc15b147d35b4cb7ca99a9a7d79d41ca342c13; version=8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a <dc6f3295905d7185e71091870119a8c11c3808cc; version=967faa26f313a62e7bebc55d5b8122eaee43b929

Published CVSS scores

7.5LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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