CVE-2026-89547
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk45th percentile - higher than 45% of all known CVEs
Summary
In the Linux kernel, __svc_create() ignored the return values of percpu_counter_init() when initializing three per-pool RPC statistics counters. When a per-CPU allocation fails (e.g., under memory pressure), the RPC service (nfsd, lockd, or NFS callback service) is started with uninitialized counters whose per-CPU pointer is NULL. This silently corrupts data in the current CPU's per-CPU area and causes /proc/fs/nfsd/pool_stats to return garbage.
Risk Assessment
The vulnerability can lead to silent kernel memory corruption and system instability, but triggering it requires a local administrator and a per-CPU allocation failure (memory pressure or fault injection). A remote peer cannot induce this state on its own.
Recommendation
Update the Linux kernel to a version containing the fix that checks percpu_counter_init() return values in __svc_create() and properly unwinds already-initialized counters on failure. Until patched, monitor memory usage on NFS/RPC servers and avoid extreme memory pressure conditions.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Check svc pool percpu counter allocation __svc_create() initializes three per-pool percpu_counter stats and ignores every return value. On SMP, percpu_counter_init() fails when __alloc_percpu_gfp() cannot satisfy the allocation, leaving the failed counter with fbc->counters == NULL and its embedded raw_spinlock_t, list_head, and count never initialized. __svc_create() returns the half-constructed svc_serv to nfsd, lockd, or the NFS callback service anyway. Once that service is live, the hot-path increments in svc_xprt_enqueue(), svc_handle_xprt(), and svc_pool_wake_idle_thread() reach a counter whose backing pointer is NULL. The pointer is a per-cpu offset, so the access does not fault: it resolves to offset zero of the current CPU's per-cpu area and silently corrupts whatever variable lives there. A /proc/fs/nfsd/pool_stats read walks the same NULL per-cpu storage and returns garbage, and on CONFIG_DEBUG_SPINLOCK or lockdep it splats on the never-initialized lock. Creating the broken service requires a percpu allocation failure during RPC server startup, so it is reachable only by a local administrator under memory pressure or fault injection; a remote peer cannot induce the bad state on its own. Check each percpu_counter_init() return value in __svc_create() and fail when an allocation fails, unwinding the counters already set up in the current pool and in every pool initialized before it. A discrete percpu_counter_destroy() per counter at teardown frees each per-cpu allocation exactly once.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS