NFS: Return a delegation the client fails to record
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 7 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
In the Linux kernel, the following vulnerability has been resolved: NFS: Return a delegation the client fails to record When an NFS server grants a delegation in an OPEN reply, nfs_inode_set_delegation() records it on the client. However, three of its error flows return without sending DELEGRETURN. A delegation can be relinquished only by DELEGRETURN (RFC 8881 Section 20.2.4), so dropping one silently leaves the server believing the client still holds it. If the server happens to recall that delegation, the client answers CB_RECALL with NFS4ERR_BADHANDLE because it has no record of the stateid. The server revokes the delegation and moves it onto its cl_revoked list, because the client never sends the FREE_STATEID that would drain it. Every subsequent SEQUENCE reply then carries SEQ4_STATUS_RECALLABLE_STATE_REVOKED, and the client's state manager loops issuing TEST_STATEID across its delegations without ever clearing the condition. The window is easy to reach now that a server offers a write delegation on any write OPEN: a delegation recalled for one opener races a re-open that the server answers with a fresh write delegation. Instead of dropping it, hand the delegation back during these error flows.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 6.1.191, 6.6.160, 6.12.114, 6.18.57, 7.2.6, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-90234
- 2026-10-03 Alias added: GHSA-qx9f-2gch-8fvp
- 2026-10-15 Affected versions changed · Red Hat
- 2026-10-15 CVSS score added · Red Hat
- 2026-10-16 Fix available: Linux/[email protected], Linux/Linux@6822ba1ae9b6df6a094f7f8998f1da734c85fa19 · CNA
- 2026-10-16 1 new reference · CNA
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-21 Affected versions changed · Red Hat
- 2026-10-21 CVSS score changed · Red Hat
- 2026-10-21 Fix available: Linux/[email protected], Linux/[email protected], Linux/Linux@9e71e332fa2c7a48f3d00001f856a13cc2d69639 +1 · CNA
- 2026-10-21 2 new references · CNA
- 2026-10-28 EPSS moved to the 50th–90th percentile
- 2026-10-30 Fix available: Linux/[email protected], Linux/Linux@61b23f482b2082e77d2f78bd1624f93a12ec35ce · CNA
- 2026-10-30 1 new reference · CNA
- 2026-10-30 Affected versions changed · Red Hat
References
Other 6
- https://git.kernel.org/stable/c/61b23f482b2082e77d2f78bd1624f93a12ec35ce
- https://git.kernel.org/stable/c/9e71e332fa2c7a48f3d00001f856a13cc2d69639
- https://git.kernel.org/stable/c/fe3b1c8966a27b70599d28ce7e80819adac1ff22
- https://git.kernel.org/stable/c/6822ba1ae9b6df6a094f7f8998f1da734c85fa19
- https://git.kernel.org/stable/c/92533e49fe3c455088657b862cf3562260c0ce25
- https://git.kernel.org/stable/c/220af23d863995091f0edeb1e6aa0945b3db8b37
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Sources
- CVE-2026-90234 · CVE Program
- CVE-2026-90234 · NVD
- FIRST EPSS
- GHSA-qx9f-2gch-8fvp · GitHub Advisory Database · CC BY 4.0
- CVE-2026-90234 · Red Hat security data · CC BY 4.0
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