{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.19.8-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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++] = 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.",
  "id": "DEBIAN-CVE-2026-23342",
  "modified": "2026-09-14T16:47:28.812873743Z",
  "published": "2026-03-25T11:16:32.147Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-23342"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-23342"
  ]
}