{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74267","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-08-15T05:44:03.878Z","datePublished":"2026-08-15T05:57:42.263Z","dateUpdated":"2026-08-17T05:45:13.330Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T05:45:13.330Z"},"descriptions":[{"lang":"en","value":"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_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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - Remote senders reach the bug when packets traverse a QFQ (or other qlen_notify parent) with a codel child: qfq_enqueue() and qfq_dequeue() call the child peek handler during __dev_queue_xmit scheduling, and CoDel can drop there before qlen is restored.\nAC:L - The attacker controls traffic rate, packet size, and CoDel drop behavior to force drops during peek while qlen reads zero; this is a deterministic logic bug, not a race on uncontrollable kernel state or a rare compile-time configuration.\nPR:N - On systems where an operator has already deployed a parent qdisc with a codel child, any remote party that can send packets into the shaped class can trigger the faulty peek/drop path with no account or capabilities on the victim host.\nUI:N - Exploitation requires only attacker-generated traffic (and, for full crash during teardown, attacker-initiated tc reconfiguration); no independent action by another user or administrator is needed at trigger time.\nS:U - The flaw corrupts in-kernel QFQ/CoDel scheduler structures and memory within the same kernel security domain; it does not cross VM, container, or IOMMU authority boundaries.\nC:H - False qlen_notify prematurely deactivates QFQ aggregates while packets remain; the fix commit shows KASAN wild-memory-access on poisoned aggregate list nodes in qfq_deactivate_agg(), giving attacker-influenced reads from freed/corrupted scheduler memory.\nI:H - Corrupted aggregate/class linkage leads to invalid hlist operations and inconsistent scheduler state that can be steered with heap layout control, yielding memory corruption primitives usable for arbitrary kernel writes or control-flow hijack.\nA:H - The published oops is a general protection fault from corrupted QFQ state during qdisc teardown, and the same corruption during live packet scheduling can reliably kernel-panic or hang affected hosts."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_codel.c"],"versions":[{"version":"cc71a757da78dd4aa1b4a9b19cb011833730ccf2","lessThan":"bb9cfd874ee884117b33e92a002b9a45b48202f4","status":"affected","versionType":"git"},{"version":"eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450","lessThan":"7a05af7f58566682b73578b72ca8e53a268c43bd","status":"affected","versionType":"git"},{"version":"829c49b6b2ff45b043739168fd1245e4e1a91a30","lessThan":"eba49fd85995a3851c597fa2d214f8d21736e1d8","status":"affected","versionType":"git"},{"version":"2f9761a94bae33d26e6a81b31b36e7d776d93dc1","lessThan":"e8c6dbadf139cb14ea6ed14add6ed6e88504dedd","status":"affected","versionType":"git"},{"version":"4d55144b12e742404bb3f8fee6038bafbf45619d","lessThan":"e4615aa6bb7802944ae790cb4b3ef8c1b7491af3","status":"affected","versionType":"git"},{"version":"342debc12183b51773b3345ba267e9263bdfaaef","lessThan":"755108bb7a5083e911294c416cfea605dc75632f","status":"affected","versionType":"git"},{"version":"342debc12183b51773b3345ba267e9263bdfaaef","lessThan":"91e0a793a72374c20ab31a40ccec21373e82e973","status":"affected","versionType":"git"},{"version":"342debc12183b51773b3345ba267e9263bdfaaef","lessThan":"52f1da34c9f4d5bdc1e8b44242da5c7ba8db85f3","status":"affected","versionType":"git"},{"version":"7a742a9506849d1c1aa71e36c89855ceddc7d58e","status":"affected","versionType":"git"},{"version":"e73c838c80dccb9e4f19becc11d9f3cb4a27d483","status":"affected","versionType":"git"},{"version":"a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31","status":"affected","versionType":"git"},{"version":"5.10.241","lessThan":"5.10.261","status":"affected","versionType":"semver"},{"version":"5.15.190","lessThan":"5.15.212","status":"affected","versionType":"semver"},{"version":"6.1.135","lessThan":"6.1.178","status":"affected","versionType":"semver"},{"version":"6.6.88","lessThan":"6.6.145","status":"affected","versionType":"semver"},{"version":"6.12.24","lessThan":"6.12.97","status":"affected","versionType":"semver"},{"version":"5.4.297","lessThan":"5.5","status":"affected","versionType":"semver"},{"version":"6.13.12","lessThan":"6.14","status":"affected","versionType":"semver"},{"version":"6.14.3","lessThan":"6.15","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_codel.c"],"versions":[{"version":"6.15","status":"affected"},{"version":"0","lessThan":"6.15","status":"unaffected","versionType":"semver"},{"version":"5.10.261","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.212","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.178","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.145","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.97","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.40","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.5","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.241","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.190","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.135","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.88","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.24","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.297"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14.3"}]}]}],"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"}],"title":"net/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen","x_generator":{"engine":"bippy-1.2.0"}}}}