EUVD-2026-76593
GHSA-3x6w-r97p-5874
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Authenticated NFS client (PR:L) winning a timing race (AC:H) leaks stateids causing only memory-exhaustion DoS (A:H), with no confidentiality or integrity impact.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix layout fence worker double-reference race
The workqueue core clears WORK_STRUCT_PENDING before the callback is invoked, so delayed_work_pending() in lm_breaker_timedout() can return false while the fence worker is already running. This lets the breaker take a duplicate sc_count reference and schedule a new worker that coalesces with the in-progress one. The extra reference is never put, leaking the layout stateid.
Replace the racy delayed_work_pending() check with an ls_fence_inflight boolean set atomically with refcount_inc_not_zero() under ls_lock, and cleared under ls_lock before the final nfs4_put_stid() on the dispose path; the retry path intentionally retains it. Remove the self-rearm mod_delayed_work() at the top of the worker.
AnalysisAI
Denial of service in the Linux kernel NFS server (nfsd) pNFS layout subsystem allows an authenticated NFSv4.1+ client to leak layout stateids, gradually exhausting kernel memory. A race in the layout fence/recall path (lm_breaker_timedout) lets the block-lease breaker acquire a duplicate sc_count reference that is never released, pinning the layout stateid forever. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires an nfsd server that exports pNFS layouts (the layout recall/fence path only exists in that configuration) and an authenticated NFSv4.1+ client that can obtain a layout and drive it into the lm_breaker_timedout() lease-break path. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The signals conflict sharply with the headline severity. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: upgrade to Linux 7.2.4 or 7.3-rc1 (or a distribution kernel that has backported fix commits a278d361e0e8 / 8580571227451), which replace the racy delayed_work_pending() check with the ls_fence_inflight flag under ls_lock. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify which Linux kernel versions power your NFS servers and verify whether NFSv4.1+ pNFS exports are enabled by checking running kernel version with uname -r and configuration with grep -i pnfs /etc/exports. …
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