--- id: CVE-2026-80630 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_reduc… summary: >- 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_reduc… severity: critical cvss: 9.8 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-664 vendor: Linux product: Linux affected: - >- Linux >= cc71a757da78dd4aa1b4a9b19cb011833730ccf2 < 3e515188393e62a718ccebee651ee74514104ff6 - >- Linux >= eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 < 20dd591d8f951e1e6aca5052be8785e6181055e2 - >- Linux >= 829c49b6b2ff45b043739168fd1245e4e1a91a30 < 94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80 - >- Linux >= 2f9761a94bae33d26e6a81b31b36e7d776d93dc1 < acc08a0c7f37ebb1901144e03a7cba7d4afd9203 - >- Linux >= 4d55144b12e742404bb3f8fee6038bafbf45619d < 7c09843fd2b44d9bf0de798683861d1aecd62a08 - >- Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 0500af8630c3253f0dde879bd3a73a06bb2f2b3f - >- Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < af54df2f44d9605614bc7ed96640302a240a9a62 - >- Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 097f6fc7b1ae362dd7a9444b2572162fda73b284 - Linux 7a742a9506849d1c1aa71e36c89855ceddc7d58e - Linux e73c838c80dccb9e4f19becc11d9f3cb4a27d483 - Linux a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31 - Linux >= 5.10.241 < 5.10.261 - Linux >= 5.15.190 < 5.15.212 - Linux >= 6.1.135 < 6.1.178 - Linux >= 6.6.88 < 6.6.145 - Linux >= 6.12.24 < 6.12.97 - Linux >= 5.4.297 < 5.5 - Linux >= 6.13.12 < 6.14 - Linux >= 6.14.3 < 6.15 - Linux 6.15 published: '2026-08-28' updated: '2026-10-16' sourceUpdated: '2026-10-16T20:18:04.520' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80630' references: - url: 'https://git.kernel.org/stable/c/0500af8630c3253f0dde879bd3a73a06bb2f2b3f' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/097f6fc7b1ae362dd7a9444b2572162fda73b284' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/20dd591d8f951e1e6aca5052be8785e6181055e2' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/3e515188393e62a718ccebee651ee74514104ff6' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/7c09843fd2b44d9bf0de798683861d1aecd62a08' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/94a5f1efdefb01f82cd228bf4e7ef1e8fc075c80' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/acc08a0c7f37ebb1901144e03a7cba7d4afd9203' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/af54df2f44d9605614bc7ed96640302a240a9a62' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80630.json - url: 'https://access.redhat.com/security/cve/CVE-2026-80630' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2525457' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-80630' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80630' - url: 'https://kernelcve.org/list/?q=CVE-2026-80630' - url: >- https://lore.kernel.org/linux-cve-announce/2026082838-CVE-2026-80630-9d99@gregkh/T tags: - nvd - cve.org - csaf - vex - red-hat - score-dispute epss: 0.00755 epssPercentile: 0.54916 ssvc: exploitation: none automatable: 'yes' technicalImpact: total timestamp: '2026-10-16T19:19:03.830771Z' scores: nvd: 9.8 vendor: 5.5 ingestedAt: '2026-08-29T23:43:56.447Z' --- ## Overview 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. An issue arises because it calls qdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops to zero, but peek returns an skb, the parent's qlen_notify callback will be executed even though fq_codel still has 1 packet on the queue and, thus, will mistakenly deactivate the parent's class causing issues like a recent report [1] and a wild memory access in qfq: [ 29.371146][ T360] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI [ 29.371666][ T360] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127] [ 29.371987][ T360] CPU: 6 UID: 0 PID: 360 Comm: tc Not tainted 7.1.0-rc5-00285-gc530e5b2dbc6-dirty #82 PREEMPT(full) [ 29.372384][ T360] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 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 [ 29.373544][ T360] RSP: 0018:ffff888102417370 EFLAGS: 00010216 [ 29.373800][ T360] RAX: 0000000000000000 RBX: ffff88811224d568 RCX: dffffc0000000000 [ 29.374079][ T360] RDX: 1ffff11021fe1543 RSI: ffff88810ff0aa00 RDI: dffffc0000000000 [ 29.374368][ T360] RBP: ffff88811224c280 R08: dead000000000122 R09: 1bd5a00000000024 [ 29.374649][ T360] R10: fffffbfff7940329 R11: fffffbfff7940329 R12: 0000000000000000 [ 29.374926][ T360] R13: dead000000000100 R14: ffff88811224d580 R15: ffff88811224d578 [ 29.375207][ T360] FS: 00007f5b794e5780(0000) GS:ffff88815d1e9000(0000) knlGS:0000000000000000 [ 29.375545][ T360] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 29.375823][ T360] CR2: 000055ffb091f000 CR3: 000000010a305000 CR4: 0000000000750ef0 [ 29.376103][ T360] PKRU: 55555554 [ 29.376258][ T360] Call Trace: [ 29.376401][ T360] ... [ 29.376885][ T360] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq [ 29.377074][ T360] qdisc_reset (net/sched/sch_generic.c:1057) [ 29.377414][ T360] __qdisc_destroy (net/sched/sch_generic.c:1096) [ 29.377600][ T360] qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159) [ 29.378593][ T360] tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556) Fix this by only calling qdisc_tree_reduce_backlog in peek after the qlen is restored. [1] http://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/ ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80630.json)