CVE-2025-38231: nfsd: Initialize ssc before laundromat_work to prevent NULL dereference

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-04 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: Initialize ssc before laundromat_work to prevent NULL dereference In nfs4_state_start_net(), laundromat_work may access nfsd_ssc through nfs4_laundromat -> nfsd4_ssc_expire_umount. If nfsd_ssc isn't initialized, this can cause NULL pointer dereference. Normally the delayed start of laundromat_work allows sufficient time for nfsd_ssc initialization to complete. However, when the kernel waits too long for userspace responses (e.g. in nfs4_state_start_net -> nfsd4_end_grace -> nfsd4_record_grace_done -> nfsd4_cld_grace_done -> cld_pipe_upcall -> __cld_pipe_upcall -> wait_for_completion path), the delayed work may start before nfsd_ssc initialization finishes. Fix this by moving nfsd_ssc initialization before starting laundromat_work.

Affected products

Debian Linux: 11.0
Linux kernel: from 5.10.220 before 5.10.239; from 5.14 before 5.15.186; from 5.16 before 6.1.142; from 6.2 before 6.6.95; from 6.7 before 6.12.35; from 6.13 before 6.15.4 — fixed in 5.10.239, 5.15.186, 6.1.142, 6.12.35, 6.15.4, 6.6.95

How to fix

Upgrade to a fixed version: Linux kernel 5.10.239, 5.15.186, 6.1.142, 6.12.35. Check the vendor advisory for mitigations.

References

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