{
  "cveId": "CVE-2026-23342",
  "url": "https://patchblox.com/security/cve/CVE-2026-23342",
  "summary": "CVE-2026-23342 is fixed in 23 products on 1 platform, first by DEBIAN-CVE-2026-23342, released March 25, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  bpf: Fix race in cpumap on PREEMPT_RT  On PREEMP...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  bpf: Fix race in cpumap on PREEMPT_RT  On PREEMPT_RT kernels, the per-CPU xdp_bulk_queue (bq) can be accessed concurrently by multiple preemptible tasks on the same CPU.  The original code assumes bq_enqueue() and __cpu_map_flush() run atomically with respect to each other on the same CPU, relying on local_bh_disable() to prevent preemption. However, on PREEMPT_RT, local_bh_disable() only calls migrate_disable() (when PREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable preemption, which allows CFS scheduling to preempt a task during bq_flush_to_queue(), enabling another task on the same CPU to enter bq_enqueue() and operate on the same per-CPU bq concurrently.  This leads to several races:  1. Double __list_del_clearprev(): after bq-\u003Ecount is reset in    bq_flush_to_queue(), a preempting task can call bq_enqueue() -\u003E    bq_flush_to_queue() on the same bq when bq-\u003Ecount reaches    CPU_MAP_BULK_SIZE. Both tasks then call __list_del_clearprev()    on the same bq-\u003Eflush_node, the second call dereferences the    prev pointer that was already set to NULL by the first.  2. bq-\u003Ecount and bq-\u003Eq[] races: concurrent bq_enqueue() can corrupt    the packet queue while bq_flush_to_queue() is processing it.  The race between task A (__cpu_map_flush -\u003E bq_flush_to_queue) and task B (bq_enqueue -\u003E bq_flush_to_queue) on the same CPU:    Task A (xdp_do_flush)          Task B (cpu_map_enqueue)   ----------------------         ------------------------   bq_flush_to_queue(bq)     spin_lock(\u0026q-\u003Eproducer_lock)     /* flush bq-\u003Eq[] to ptr_ring */     bq-\u003Ecount = 0     spin_unlock(\u0026q-\u003Eproducer_lock)                                    bq_enqueue(rcpu, xdpf)     \u003C-- CFS preempts Task A --\u003E      bq-\u003Eq[bq-\u003Ecount\u002B\u002B] = xdpf                                      /* ... more enqueues until full ... */                                      bq_flush_to_queue(bq)                                        spin_lock(\u0026q-\u003Eproducer_lock)                                        /* flush to ptr_ring */                                        spin_unlock(\u0026q-\u003Eproducer_lock)                                        __list_del_clearprev(flush_node)                                          /* sets flush_node.prev = NULL */     \u003C-- Task A resumes --\u003E     __list_del_clearprev(flush_node)       flush_node.prev-\u003Enext = ...       /* prev is NULL -\u003E kernel oops */  Fix this by adding a local_lock_t to xdp_bulk_queue and acquiring it in bq_enqueue() and __cpu_map_flush(). These paths already run under local_bh_disable(), so use local_lock_nested_bh() which on non-RT is a pure annotation with no overhead, and on PREEMPT_RT provides a per-CPU sleeping lock that serializes access to the bq.  To reproduce, insert an mdelay(100) between bq-\u003Ecount = 0 and __list_del_clearprev() in bq_flush_to_queue(), then run reproducer provided by syzkaller.",
  "published": "2026-03-25T11:16:32Z",
  "severity": "medium",
  "cvss": 4.7,
  "cvssVector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00091,
  "epssPercentile": 0.00473,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "bpftool6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.20-20.229.amzn2023",
      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "product": "bpftool6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.20-20.229.amzn2023",
      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel-livepatch-6.18.20-20.229",
      "release": "amzn 2023",
      "fixedVersion": "1:1.0-0.amzn2023",
      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
      "fixedVersion": "1:6.18.20-20.229.amzn2023",
      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
      "fixedVersion": "1:6.18.20-20.229.amzn2023",
      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "product": "kernel6.18-debuginfo-common-aarch64",
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
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    {
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
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      "fix": "ALAS2023-2026-1596",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1596",
      "released": "2026-04-27T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "6.19.8-1",
      "fix": "DEBIAN-CVE-2026-23342",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-23342",
      "released": "2026-03-25T11:16:32Z"
    },
    {
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      "release": "amzn 2023",
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
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      "released": "2026-04-27T09:00:00Z"
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      "fix": "ALAS2023-2026-1596",
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      "released": "2026-04-27T09:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}