{"id":"CVE-2026-74267","title":"net/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen\n\nWhenever codel drops packets during peek, it calls\nqdisc_tree_reduce_back…","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","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= cc71a757da78dd4aa1b4a9b19cb011833730ccf2 < bb9cfd874ee884117b33e92a002b9a45b48202f4","Linux >= eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 < 7a05af7f58566682b73578b72ca8e53a268c43bd","Linux >= 829c49b6b2ff45b043739168fd1245e4e1a91a30 < eba49fd85995a3851c597fa2d214f8d21736e1d8","Linux >= 2f9761a94bae33d26e6a81b31b36e7d776d93dc1 < e8c6dbadf139cb14ea6ed14add6ed6e88504dedd","Linux >= 4d55144b12e742404bb3f8fee6038bafbf45619d < e4615aa6bb7802944ae790cb4b3ef8c1b7491af3","Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 755108bb7a5083e911294c416cfea605dc75632f","Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 91e0a793a72374c20ab31a40ccec21373e82e973","Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 52f1da34c9f4d5bdc1e8b44242da5c7ba8db85f3","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"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T18:51:44.190573Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:55:28.845Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74267","references":[{"url":"https://git.kernel.org/stable/c/bb9cfd874ee884117b33e92a002b9a45b48202f4"},{"url":"https://git.kernel.org/stable/c/7a05af7f58566682b73578b72ca8e53a268c43bd"},{"url":"https://git.kernel.org/stable/c/eba49fd85995a3851c597fa2d214f8d21736e1d8"},{"url":"https://git.kernel.org/stable/c/e8c6dbadf139cb14ea6ed14add6ed6e88504dedd"},{"url":"https://git.kernel.org/stable/c/e4615aa6bb7802944ae790cb4b3ef8c1b7491af3"},{"url":"https://git.kernel.org/stable/c/755108bb7a5083e911294c416cfea605dc75632f"},{"url":"https://git.kernel.org/stable/c/91e0a793a72374c20ab31a40ccec21373e82e973"},{"url":"https://git.kernel.org/stable/c/52f1da34c9f4d5bdc1e8b44242da5c7ba8db85f3"}],"tags":["cve.org"],"epss":0.00714,"epssPercentile":0.52757,"ingestedAt":"2026-10-16T19:46:24.387Z","slug":"CVE-2026-74267","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen\n\nWhenever 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\nbe executed even though codel still has 1 packet on the queue and, thus,\nwill mistakenly deactivate the parent's class causing issues like a wild\nmemory access when qfq has codel as a child:\n\n[   36.339843][  T370] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI\n[   36.340408][  T370] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]\n[   36.340737][  T370] CPU: 2 UID: 0 PID: 370 Comm: tc Not tainted 7.1.0-rc5-00287-g66e13b626592 #87 PREEMPT(full)\n[   36.341113][  T370] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011\n[   36.341357][  T370] 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[   36.342221][  T370] RSP: 0018:ffff8881100ef370 EFLAGS: 00010216\n[   36.342422][  T370] RAX: 0000000000000000 RBX: ffff8881058a9568 RCX: dffffc0000000000\n[   36.342664][  T370] RDX: 1ffff11021064dc3 RSI: ffff888108326e00 RDI: dffffc0000000000\n[   36.342905][  T370] RBP: ffff8881058a8280 R08: dead000000000122 R09: 1bd5a00000000024\n[   36.343140][  T370] R10: fffffbfff2940329 R11: fffffbfff2940329 R12: 0000000000000000\n[   36.343383][  T370] R13: dead000000000100 R14: ffff8881058a9580 R15: ffff8881058a9578\n[   36.343631][  T370] FS:  00007fc04b0ca780(0000) GS:ffff888184fef000(0000) knlGS:0000000000000000\n[   36.343911][  T370] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   36.344116][  T370] CR2: 0000557c02c02000 CR3: 000000010e0ba000 CR4: 0000000000750ef0\n[   36.344359][  T370] PKRU: 55555554\n[   36.344481][  T370] Call Trace:\n...\n[   36.345054][  T370] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq\n[   36.345222][  T370]  qdisc_reset (net/sched/sch_generic.c:1057)\n[   36.345503][  T370]  __qdisc_destroy (net/sched/sch_generic.c:1096)\n[   36.345677][  T370]  qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159)\n[   36.346335][  T370]  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## Affected\n\n- `Linux >= cc71a757da78dd4aa1b4a9b19cb011833730ccf2 < bb9cfd874ee884117b33e92a002b9a45b48202f4`\n- `Linux >= eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 < 7a05af7f58566682b73578b72ca8e53a268c43bd`\n- `Linux >= 829c49b6b2ff45b043739168fd1245e4e1a91a30 < eba49fd85995a3851c597fa2d214f8d21736e1d8`\n- `Linux >= 2f9761a94bae33d26e6a81b31b36e7d776d93dc1 < e8c6dbadf139cb14ea6ed14add6ed6e88504dedd`\n- `Linux >= 4d55144b12e742404bb3f8fee6038bafbf45619d < e4615aa6bb7802944ae790cb4b3ef8c1b7491af3`\n- `Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 755108bb7a5083e911294c416cfea605dc75632f`\n- `Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 91e0a793a72374c20ab31a40ccec21373e82e973`\n- `Linux >= 342debc12183b51773b3345ba267e9263bdfaaef < 52f1da34c9f4d5bdc1e8b44242da5c7ba8db85f3`\n- `Linux 7a742a9506849d1c1aa71e36c89855ceddc7d58e`\n- `Linux e73c838c80dccb9e4f19becc11d9f3cb4a27d483`\n- `Linux a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31`\n- `Linux >= 5.10.241 < 5.10.261`\n- `Linux >= 5.15.190 < 5.15.212`\n- `Linux >= 6.1.135 < 6.1.178`\n- `Linux >= 6.6.88 < 6.6.145`\n- `Linux >= 6.12.24 < 6.12.97`\n- `Linux >= 5.4.297 < 5.5`\n- `Linux >= 6.13.12 < 6.14`\n- `Linux >= 6.14.3 < 6.15`\n- `Linux 6.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}