CVE-2026-90037: NFSD: Prevent client use-after-free during close_lru reaping

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-16 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during close_lru reaping An nfs4_openowner left on nn->close_lru after its final CLOSE keeps its last closed stateid in oo_last_closed_stid, holding only a raw pointer to its nfs4_client. The laundromat reaps timed-out entries, drops nn->client_lock, and calls nfs4_put_stid(), which dereferences the client through cl_lock. Nothing pins the client across that window, so a concurrent force_expire_client() can free it and nfs4_put_stid() reads freed memory. __destroy_client() hits the same race, walking clp->cl_openowners without cl_lock. Pin the client with cl_rpc_users before dropping client_lock, and skip clients already expiring. __destroy_client() then cleans up its own close_lru entries through release_last_closed_stateid(), so teardown no longer races the laundromat.

Affected products

Linux: 3.17 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

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