{"id":"DEBIAN-CVE-2026-23342","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(&q-\u003eproducer_lock)     /* flush bq-\u003eq[] to ptr_ring */     bq-\u003ecount = 0     spin_unlock(&q-\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(&q-\u003eproducer_lock)                                        /* flush to ptr_ring */                                        spin_unlock(&q-\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.","modified":"2026-09-14T17:02:42.213023528Z","published":"2026-03-25T11:16:32.147Z","upstream":["CVE-2026-23342"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-23342"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.19.8-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-23342.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}