{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  nfsd: hold rcu across localio cmpxchg retry  nfsd_file objects are freed via call_rcu (filecache.c:296), and nfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU (KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page backing a freed nfsd_file becomes freely reclaimable once the RCU grace period elapses.  The again: retry block in nfsd_open_local_fh() loads a pointer with cmpxchg and then calls nfsd_file_get(new) (which is refcount_inc_not_zero) without holding rcu_read_lock. The sole caller nfs_open_local_fh() drops rcu_read_lock before invoking this helper, so no outer reader-side critical section covers the load.      CPU 0 (nfsd_open_local_fh)        CPU 1 (nfsd_file_put_local)     -----                             -----     new = cmpxchg(pnf, NULL, ...)                                       nf = xchg(pnf, NULL)                                       nfsd_file_put(nf)                                         last ref -\u003e call_rcu()                                       /* grace period elapses;                                          slab page recycled */     nfsd_file_get(new)       refcount_inc_not_zero(\u0026new-\u003enf_ref)       /* operates on recycled memory */  A non-zero word at the nf_ref offset of the recycled object makes the refcount bump appear to succeed, and the caller then dereferences new-\u003enf_net and new-\u003enf_file out of freed memory.  Fix by taking rcu_read_lock() immediately before the cmpxchg and releasing it on all three exits of the if (new) block: the goto-again retry, the lost-race cleanup path, and the install-succeeded path. nfsd_file_put() and nfsd_net_put() stay outside the RCU section so they remain free to block.",
  "id": "DEBIAN-CVE-2026-89670",
  "modified": "2026-09-14T08:47:42.340580296Z",
  "published": "2026-09-11T20:19:53.517Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-89670"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-89670"
  ]
}