{
  "cveId": "CVE-2026-89991",
  "url": "https://patchblox.com/security/cve/CVE-2026-89991",
  "summary": "CVE-2026-89991 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-89991, released September 23, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "bpf: Fix infinite loop in pcpu_freelist push with one possible CPU",
  "description": "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\u0027s 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.",
  "published": "2026-09-16T11:17:10Z",
  "severity": "important",
  "epss": 0.00206,
  "epssPercentile": 0.10781,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89991",
  "fixes": [
    {
      "platform": "linux",
      "product": "bpftool6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "bpftool6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel-livepatch-6.18.51-120.162",
      "release": "amzn 2023",
      "fixedVersion": "1:1.0-0.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-aarch64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-x86_64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-headers",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra-common",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.6-1",
      "fix": "DEBIAN-CVE-2026-89991",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-89991",
      "released": "2026-09-23T19:19:02Z"
    },
    {
      "platform": "linux",
      "product": "microvm-kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.51-120.162.amzn2023",
      "fix": "ALAS2023-2026-3187",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3187",
      "released": "2026-11-07T01:06:52Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T00:53:09Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}