{ "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" } } } }