CVE-2026-98369 (GCVE-0-2026-98369)
Vulnerability from cvelistv5
Published
2026-10-06 08:46
Modified
2026-10-19 09:18
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject() syzbot reported a suspicious RCU usage warning in ip6_pkt_drop(): WARNING: suspicious RCU usage in ip6_pkt_drop include/net/addrconf.h:389 suspicious rcu_dereference_check() usage! Call Trace: __in6_dev_get_safely include/net/addrconf.h:389 [inline] ip6_pkt_drop+0x596/0x610 net/ipv6/route.c:4620 ip6_pkt_discard+0x1c/0x30 net/ipv6/route.c:4651 xfrm_trans_reinject+0x324/0x630 net/xfrm/xfrm_input.c:806 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 When commit 4f4920669d21 ("xfrm: Reinject transport-mode packets through workqueue") converted xfrm_trans_reinject from a tasklet to a workqueue, the reinjection loop ceased running in softirq context. Workqueue workers run in process context where local_bh_disable() does not enter an RCU read-side critical section under CONFIG_PREEMPT_RCU. Because finish callbacks (such as ip6_rcv_finish) expect to run under an RCU read lock (performing route lookups, l3mdev lookups, and accessing RCU-protected data structures), invoking them in workqueue context without rcu_read_lock() triggers RCU lockdep warnings. Furthermore, packets queued to the workqueue via xfrm_trans_queue_net() may carry non-refcounted (noref) dst entries (e.g. from ip_route_input_noref). Additionally, on netdevice unregistration, dst_dev_put() replaces dst->dev with blackhole_netdev, so dst entries do not keep skb->dev alive while queued in the workqueue. Fix these issues by: 1. Calling skb_dst_force(skb) in xfrm_trans_queue_net() while still in the caller's RCU section to ensure dst is reference-counted before queuing. 2. Holding a reference on skb->dev via dev_hold()/dev_put() across workqueue deferral so skb->dev remains valid during finish() callback processing. 3. Acquiring rcu_read_lock() around the finish callback invocation loop in xfrm_trans_reinject().
References
Impacted products
Vendor Product Version
Linux Linux Version: 7d98b26684cb2390729525b341ea099f0badbe18
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: 4f4920669d21e1060b7243e5118dc3b71ced1276
Version: f520075da484306bbb8425afd2c42404ba74816f
Version: 130d9e5017ade1b81d16783563edb38c12a2eab7
Version: 5.15.75   ≤
Version: 5.19.17   ≤
Version: 6.0.3   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject()\n\nsyzbot reported a suspicious RCU usage warning in ip6_pkt_drop():\n\n  WARNING: suspicious RCU usage in ip6_pkt_drop\n  include/net/addrconf.h:389 suspicious rcu_dereference_check() usage!\n\n  Call Trace:\n   __in6_dev_get_safely include/net/addrconf.h:389 [inline]\n   ip6_pkt_drop+0x596/0x610 net/ipv6/route.c:4620\n   ip6_pkt_discard+0x1c/0x30 net/ipv6/route.c:4651\n   xfrm_trans_reinject+0x324/0x630 net/xfrm/xfrm_input.c:806\n   process_one_work kernel/workqueue.c:3322 [inline]\n   process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405\n   worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486\n\nWhen commit 4f4920669d21 (\"xfrm: Reinject transport-mode packets through\nworkqueue\") converted xfrm_trans_reinject from a tasklet to a workqueue,\nthe reinjection loop ceased running in softirq context. Workqueue workers\nrun in process context where local_bh_disable() does not enter an RCU\nread-side critical section under CONFIG_PREEMPT_RCU.\n\nBecause finish callbacks (such as ip6_rcv_finish) expect to run under an\nRCU read lock (performing route lookups, l3mdev lookups, and accessing\nRCU-protected data structures), invoking them in workqueue context without\nrcu_read_lock() triggers RCU lockdep warnings.\n\nFurthermore, packets queued to the workqueue via xfrm_trans_queue_net()\nmay carry non-refcounted (noref) dst entries (e.g. from ip_route_input_noref).\nAdditionally, on netdevice unregistration, dst_dev_put() replaces dst-\u003edev\nwith blackhole_netdev, so dst entries do not keep skb-\u003edev alive while\nqueued in the workqueue.\n\nFix these issues by:\n1. Calling skb_dst_force(skb) in xfrm_trans_queue_net() while still in the\n   caller\u0027s RCU section to ensure dst is reference-counted before queuing.\n2. Holding a reference on skb-\u003edev via dev_hold()/dev_put() across workqueue\n   deferral so skb-\u003edev remains valid during finish() callback processing.\n3. Acquiring rcu_read_lock() around the finish callback invocation loop in\n   xfrm_trans_reinject()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The use-after-free happens only when a queued packet\u0027s net_device or noref dst is freed before xfrm_trans_reinject() runs. A remote ESP peer sends the packet but cannot unregister the device or change routes, so the attacker who controls the whole race is local: they create the netns, veth and XFRM SA through xfrm_user netlink.\nAC:L - The attacker does both sides of the race. They send ESP transport-mode packets that xfrm4_transport_finish/xfrm6_transport_finish queue through xfrm_trans_queue(), then delete the veth or route while the workqueue is still behind. Flooding the queue up to max_backlog widens the window.\nPR:L - xfrm_user_rcv_msg checks netlink_net_capable(CAP_NET_ADMIN), which an unprivileged user gets in a new user and network namespace (unshare -Urn). That lets them create the SA, the veth devices and the routes the trigger needs.\nUI:N - No victim action is needed. The attacker sets up the namespace, sends the packets and tears down the device or route themselves.\nS:U - The freed net_device, dst_entry and RCU-protected route data are kernel memory, and the impact stays within the kernel\u0027s own security authority.\nC:H - ip6_rcv_finish and dst_input in xfrm_trans_reinject() read a freed skb-\u003edev or noref dst_entry with no reference and no RCU lock. If an attacker reclaims that memory, these use-after-free reads can leak kernel memory.\nI:H - The freed dst_entry holds an input function pointer that dst_input() calls, and net_device is full of ops pointers. Reclaiming either object with attacker-controlled data gives a path to hijacking control flow.\nA:H - A use-after-free of the net_device or dst in the xfrm_trans_reinject worker crashes the kernel, and syzbot hit the missing-RCU path in ip6_pkt_drop. The attacker can trigger it repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:18:21.221Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/41e47f1664be86c91326f0afe0504a1162d00907"
        },
        {
          "url": "https://git.kernel.org/stable/c/6601d91a85761f33351c71e04ec0bbd294ca07ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/0cda8273265d30cac6423834fd7d4acb75f04fdb"
        },
        {
          "url": "https://git.kernel.org/stable/c/68a317b4aec8ca1868a39d69e40f9e29baa4f40a"
        },
        {
          "url": "https://git.kernel.org/stable/c/6eb3b071be8e260543c604550c54dac66e6b174b"
        },
        {
          "url": "https://git.kernel.org/stable/c/664fc0941df7c1918b2cd4de6ee00469ba77d8e4"
        },
        {
          "url": "https://git.kernel.org/stable/c/d2f5082f9e84653fa1a9e8aebaaff23e688f5e19"
        }
      ],
      "title": "xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98369",
    "datePublished": "2026-10-06T08:46:54.188Z",
    "dateReserved": "2026-09-25T10:25:14.344Z",
    "dateUpdated": "2026-10-19T09:18:21.221Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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