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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-04-18 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: allow SC_STATUS_FREEABLE when searching via nfs4_lookup_stateid() The pynfs DELEG8 test fails when run against nfsd. It acquires a delegation and then lets the lease time out. It then tries to use the deleg stateid and expects to see NFS4ERR_DELEG_REVOKED, but it gets bad NFS4ERR_BAD_STATEID instead. When a delegation is revoked, it's initially marked with SC_STATUS_REVOKED, or SC_STATUS_ADMIN_REVOKED and later, it's marked with the SC_STATUS_FREEABLE flag, which denotes that it is waiting for s FREE_STATEID call. nfs4_lookup_stateid() accepts a statusmask that includes the status flags that a found stateid is allowed to have. Currently, that mask never includes SC_STATUS_FREEABLE, which means that revoked delegations are (almost) never found. Add SC_STATUS_FREEABLE to the always-allowed status flags, and remove it from nfsd4_delegreturn() since it's now always implied.

Affected products

Linux kernel: from 6.11.6 before 6.12; from 6.12.1 before 6.12.23; from 6.13 before 6.13.11; from 6.14 before 6.14.2; 6.12, 6.12-rc5, 6.12-rc6, 6.12-rc7 — fixed in 6.12, 6.12.23, 6.13.11, 6.14.2

How to fix

Upgrade to a fixed version: Linux kernel 6.12, 6.12.23, 6.13.11, 6.14.2. Check the vendor advisory for mitigations.

References

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