GHSA-86MQ-WJ5H-4FR6

Vulnerability from github – Published: 2026-05-21 15:34 – Updated: 2026-05-21 15:34
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_red: Replace direct dequeue call with peek and qdisc_dequeue_peeked

When red qdisc has children (eg qfq qdisc) whose peek() callback is qdisc_peek_dequeued(), we could get a kernel panic. When the parent of such qdiscs (eg illustrated in patch #3 as tbf) wants to retrieve an skb from its child (red in this case), it will do the following: 1a. do a peek() - and when sensing there's an skb the child can offer, then - the child in this case(red) calls its child's (qfq) peek. qfq does the right thing and will return the gso_skb queue packet. Note: if there wasnt a gso_skb entry then qfq will store it there. 1b. invoke a dequeue() on the child (red). And herein lies the problem. - red will call the child's dequeue() which will essentially just try to grab something of qfq's queue.

[ 78.667668][ T363] KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f] [ 78.667927][ T363] CPU: 1 UID: 0 PID: 363 Comm: ping Not tainted 7.1.0-rc1-00033-g46f74a3f7d57-dirty #790 PREEMPT(full) [ 78.668263][ T363] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 78.668486][ T363] RIP: 0010:qfq_dequeue+0x446/0xc90 [sch_qfq] [ 78.668718][ T363] Code: 54 c0 e8 dd 90 00 f1 48 c7 c7 e0 03 54 c0 48 89 de e8 ce 90 00 f1 48 8d 7b 48 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 <80> 3c 02 00 74 05 e8 ef a1 e1 f1 48 8b 7b 48 48 8d 54 24 58 48 8d [ 78.669312][ T363] RSP: 0018:ffff88810de573e0 EFLAGS: 00010216 [ 78.669533][ T363] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 78.669790][ T363] RDX: 0000000000000009 RSI: 0000000000000004 RDI: 0000000000000048 [ 78.670044][ T363] RBP: ffff888110dc4000 R08: ffffffffb1b0885a R09: fffffbfff6ba9078 [ 78.670297][ T363] R10: 0000000000000003 R11: ffff888110e31c80 R12: 0000001880000000 [ 78.670560][ T363] R13: ffff888110dc4150 R14: ffff888110dc42b8 R15: 0000000000000200 [ 78.670814][ T363] FS: 00007f66a8f09c40(0000) GS:ffff888163428000(0000) knlGS:0000000000000000 [ 78.671110][ T363] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 78.671324][ T363] CR2: 000055db4c6a30a8 CR3: 000000010da67000 CR4: 0000000000750ef0 [ 78.671585][ T363] PKRU: 55555554 [ 78.671713][ T363] Call Trace: [ 78.671843][ T363] [ 78.671936][ T363] ? __pfx_qfq_dequeue+0x10/0x10 [sch_qfq] [ 78.672148][ T363] ? __pfx__printk+0x10/0x10 [ 78.672322][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.672496][ T363] ? lockdep_hardirqs_on_prepare+0xa8/0x1a0 [ 78.672706][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.672875][ T363] ? trace_hardirqs_on+0x19/0x1a0 [ 78.673047][ T363] red_dequeue+0x65/0x270 [sch_red] [ 78.673217][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.673385][ T363] tbf_dequeue.cold+0xb0/0x70c [sch_tbf] [ 78.673566][ T363] __qdisc_run+0x169/0x1900

The right thing to do in #1b is to grab the skb off gso_skb queue. This patchset fixes that issue by changing #1b to use qdisc_dequeue_peeked() method instead.

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2026-43496"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-21T13:16:18Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_red: Replace direct dequeue call with peek and qdisc_dequeue_peeked\n\nWhen red qdisc has children (eg qfq qdisc) whose peek() callback is\nqdisc_peek_dequeued(), we could get a kernel panic. When the parent of such\nqdiscs (eg illustrated in patch #3 as tbf) wants to retrieve an skb from\nits child (red in this case), it will do the following:\n 1a. do a peek() - and when sensing there\u0027s an skb the child can offer, then\n     - the child in this case(red) calls its child\u0027s (qfq) peek.\n        qfq does the right thing and will return the gso_skb queue packet.\n        Note: if there wasnt a gso_skb entry then qfq will store it there.\n 1b. invoke a dequeue() on the child (red). And herein lies the problem.\n     - red will call the child\u0027s dequeue() which will essentially just\n       try to grab something of qfq\u0027s queue.\n\n[   78.667668][  T363] KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f]\n[   78.667927][  T363] CPU: 1 UID: 0 PID: 363 Comm: ping Not tainted 7.1.0-rc1-00033-g46f74a3f7d57-dirty #790 PREEMPT(full)\n[   78.668263][  T363] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011\n[   78.668486][  T363] RIP: 0010:qfq_dequeue+0x446/0xc90 [sch_qfq]\n[   78.668718][  T363] Code: 54 c0 e8 dd 90 00 f1 48 c7 c7 e0 03 54 c0 48 89 de e8 ce 90 00 f1 48 8d 7b 48 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 \u003c80\u003e 3c 02 00 74 05 e8 ef a1 e1 f1 48 8b 7b 48 48 8d 54 24 58 48 8d\n[   78.669312][  T363] RSP: 0018:ffff88810de573e0 EFLAGS: 00010216\n[   78.669533][  T363] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000\n[   78.669790][  T363] RDX: 0000000000000009 RSI: 0000000000000004 RDI: 0000000000000048\n[   78.670044][  T363] RBP: ffff888110dc4000 R08: ffffffffb1b0885a R09: fffffbfff6ba9078\n[   78.670297][  T363] R10: 0000000000000003 R11: ffff888110e31c80 R12: 0000001880000000\n[   78.670560][  T363] R13: ffff888110dc4150 R14: ffff888110dc42b8 R15: 0000000000000200\n[   78.670814][  T363] FS:  00007f66a8f09c40(0000) GS:ffff888163428000(0000) knlGS:0000000000000000\n[   78.671110][  T363] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   78.671324][  T363] CR2: 000055db4c6a30a8 CR3: 000000010da67000 CR4: 0000000000750ef0\n[   78.671585][  T363] PKRU: 55555554\n[   78.671713][  T363] Call Trace:\n[   78.671843][  T363]  \u003cTASK\u003e\n[   78.671936][  T363]  ? __pfx_qfq_dequeue+0x10/0x10 [sch_qfq]\n[   78.672148][  T363]  ? __pfx__printk+0x10/0x10\n[   78.672322][  T363]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   78.672496][  T363]  ? lockdep_hardirqs_on_prepare+0xa8/0x1a0\n[   78.672706][  T363]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   78.672875][  T363]  ? trace_hardirqs_on+0x19/0x1a0\n[   78.673047][  T363]  red_dequeue+0x65/0x270 [sch_red]\n[   78.673217][  T363]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   78.673385][  T363]  tbf_dequeue.cold+0xb0/0x70c [sch_tbf]\n[   78.673566][  T363]  __qdisc_run+0x169/0x1900\n\nThe right thing to do in #1b is to grab the skb off gso_skb queue.\nThis patchset fixes that issue by changing #1b to use qdisc_dequeue_peeked()\nmethod instead.",
  "id": "GHSA-86mq-wj5h-4fr6",
  "modified": "2026-05-21T15:34:08Z",
  "published": "2026-05-21T15:34:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43496"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/36aa34f42cb6842cf371f3a2d3e855d24fd57a50"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/458d5615272d3de535748342eb68ca492343048c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/587dcf970a525f543d8b5855d9f37a4ca97b76ef"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8d09618840b99ef00154d3e731ce9b11e096196d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ce051eede433f876d322ac3550a36a3c6fc4c231"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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