{
  "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:  bpf: Fix infinite loop in pcpu_freelist push with one possible CPU  __pcpu_freelist_push() can loop forever when only one CPU is possible and an NMI re-enters pcpu_freelist_push() while the interrupted context holds that CPU's freelist lock.  After the current-CPU fast path fails, the fallback loop walks cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or when an SMP kernel is limited to one possible CPU with nr_cpus=1 or possible_cpus=1, there are no other possible CPUs to examine. The loop therefore makes no lock acquisition attempt and can never make progress.  The following stack was observed on a UP system:    NMI context:     pcpu_freelist_push     free_htab_elem     htab_map_delete_elem     [perf-event BPF program]     __perf_event_overflow     perf_event_nmi_handler     exc_nmi    Interrupted context:     __pcpu_freelist_push     pcpu_freelist_push     free_htab_elem     htab_map_delete_elem     [raw_tp/sys_enter BPF program]     __bpf_trace_sys_enter     do_syscall_64  raw_res_spin_lock() detects the same-CPU recursive acquisition and returns -EDEADLK, but the subsequent fallback loop has no candidate head on a system with one possible CPU.  Restore the extra fallback head that existed before the rqspinlock conversion. Keep the current-CPU fast path, then try the other possible CPUs and finally the extra head. The additional head lets a push, which cannot fail without losing a preallocated element, make progress when the only per-CPU head is held by the interrupted context.  Also check the extra head from the pop path so that nodes placed there can be reused.",
  "id": "DEBIAN-CVE-2026-89991",
  "modified": "2026-09-17T04:47:38.363179337Z",
  "published": "2026-09-16T11:17:10.240Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-89991"
    }
  ],
  "upstream": [
    "CVE-2026-89991"
  ]
}