{"id":"CVE-2026-80630","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-80630","generatedAt":"2026-10-28T02:21:44.569Z","title":"In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen Whenever fq_codel drops packets during peek, it calls qdisc_tree_reduce_backlog.","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen\n\nWhenever fq_codel drops packets during peek, it calls\nqdisc_tree_reduce_backlog. An issue arises because it calls\nqdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops\nto zero, but peek returns an skb, the parent's qlen_notify callback will be\nexecuted even though fq_codel still has 1 packet on the queue and, thus,\nwill mistakenly deactivate the parent's class causing issues like a recent\nreport [1] and a wild memory access in qfq:\n\n[   29.371146][  T360] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI\n[   29.371666][  T360] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]\n[   29.371987][  T360] CPU: 6 UID: 0 PID: 360 Comm: tc Not tainted 7.1.0-rc5-00285-gc530e5b2dbc6-dirty #82 PREEMPT(full)\n[   29.372384][  T360] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011\n[   29.372620][  T360] RIP: 0010:qfq_deactivate_agg (include/linux/list.h:1029 (discriminator 2) include/linux/list.h:1043 (discriminator 2) net/sched/sch_qfq.c:1369 (discriminator 2) net/sched/sch_qfq.c:1395 (discriminator 2)) sch_qfq\n[   29.373544][  T360] RSP: 0018:ffff888102417370 EFLAGS: 00010216\n[   29.373800][  T360] RAX: 0000000000000000 RBX: ffff88811224d568 RCX: dffffc0000000000\n[   29.374079][  T360] RDX: 1ffff11021fe1543 RSI: ffff88810ff0aa00 RDI: dffffc0000000000\n[   29.374368][  T360] RBP: ffff88811224c280 R08: dead000000000122 R09: 1bd5a00000000024\n[   29.374649][  T360] R10: fffffbfff7940329 R11: fffffbfff7940329 R12: 0000000000000000\n[   29.374926][  T360] R13: dead000000000100 R14: ffff88811224d580 R15: ffff88811224d578\n[   29.375207][  T360] FS:  00007f5b794e5780(0000) GS:ffff88815d1e9000(0000) knlGS:0000000000000000\n[   29.375545][  T360] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   29.375823][  T360] CR2: 000055ffb091f000 CR3: 000000010a305000 CR4: 0000000000750ef0\n[   29.376103][  T360] PKRU: 55555554\n[   29.376258][  T360] Call Trace:\n[   29.376401][  T360]  <TASK>\n...\n[   29.376885][  T360] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq\n[   29.377074][  T360]  qdisc_reset (net/sched/sch_generic.c:1057)\n[   29.377414][  T360]  __qdisc_destroy (net/sched/sch_generic.c:1096)\n[   29.377600][  T360]  qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159)\n[   29.378593][  T360]  tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556)\n\nFix this by only calling qdisc_tree_reduce_backlog in peek after the\nqlen is restored.\n\n[1] http://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/","published":"2026-08-28T08:16:48.000Z","lastModified":"2026-10-16T20:18:05.000Z","status":"Received","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":[],"affected":[],"epss":{"score":0.00755,"percentile":0.54845,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.76%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/0500af8630c3253f0dde879bd3a73a06bb2f2b3f","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/097f6fc7b1ae362dd7a9444b2572162fda73b284","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/20dd591d8f951e1e6aca5052be8785e6181055e2","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3e515188393e62a718ccebee651ee74514104ff6","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7c09843fd2b44d9bf0de798683861d1aecd62a08","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/acc08a0c7f37ebb1901144e03a7cba7d4afd9203","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/af54df2f44d9605614bc7ed96640302a240a9a62","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-80630","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}