NFS: Return a delegation the client fails to record
CVE-2026-90234 · published 17 Sept 2026
How serious is it
- Severity: high, CVSS score 7.5 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-90234?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: ade04647dd56881e285983af3db702d56ee97e86 to < 9e71e332fa2c7a48f3d00001f856a13cc2d69639, ade04647dd56881e285983af3db702d56ee97e86 to < fe3b1c8966a27b70599d28ce7e80819adac1ff22, ade04647dd56881e285983af3db702d56ee97e86 to < 6822ba1ae9b6df6a094f7f8998f1da734c85fa19, ade04647dd56881e285983af3db702d56ee97e86 to < 92533e49fe3c455088657b862cf3562260c0ce25
- Linux Linux: 4.0
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/9e71e332fa2c7a48f3d00001f856a13cc2d69639
- git.kernel.org/stable/c/fe3b1c8966a27b70599d28ce7e80819adac1ff22
- git.kernel.org/stable/c/6822ba1ae9b6df6a094f7f8998f1da734c85fa19
- git.kernel.org/stable/c/92533e49fe3c455088657b862cf3562260c0ce25
- git.kernel.org/stable/c/220af23d863995091f0edeb1e6aa0945b3db8b37
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON