CVE-2026-74267 (GCVE-0-2026-74267)
Vulnerability from cvelistv5
Published
2026-08-15 05:57
Modified
2026-08-17 05:45
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen
Whenever 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 codel still has 1 packet on the queue and, thus,
will mistakenly deactivate the parent's class causing issues like a wild
memory access when qfq has codel as a child:
[ 36.339843][ T370] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI
[ 36.340408][ T370] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127]
[ 36.340737][ T370] CPU: 2 UID: 0 PID: 370 Comm: tc Not tainted 7.1.0-rc5-00287-g66e13b626592 #87 PREEMPT(full)
[ 36.341113][ T370] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 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
[ 36.342221][ T370] RSP: 0018:ffff8881100ef370 EFLAGS: 00010216
[ 36.342422][ T370] RAX: 0000000000000000 RBX: ffff8881058a9568 RCX: dffffc0000000000
[ 36.342664][ T370] RDX: 1ffff11021064dc3 RSI: ffff888108326e00 RDI: dffffc0000000000
[ 36.342905][ T370] RBP: ffff8881058a8280 R08: dead000000000122 R09: 1bd5a00000000024
[ 36.343140][ T370] R10: fffffbfff2940329 R11: fffffbfff2940329 R12: 0000000000000000
[ 36.343383][ T370] R13: dead000000000100 R14: ffff8881058a9580 R15: ffff8881058a9578
[ 36.343631][ T370] FS: 00007fc04b0ca780(0000) GS:ffff888184fef000(0000) knlGS:0000000000000000
[ 36.343911][ T370] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 36.344116][ T370] CR2: 0000557c02c02000 CR3: 000000010e0ba000 CR4: 0000000000750ef0
[ 36.344359][ T370] PKRU: 55555554
[ 36.344481][ T370] Call Trace:
...
[ 36.345054][ T370] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq
[ 36.345222][ T370] qdisc_reset (net/sched/sch_generic.c:1057)
[ 36.345503][ T370] __qdisc_destroy (net/sched/sch_generic.c:1096)
[ 36.345677][ T370] qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159)
[ 36.346335][ T370] 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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: cc71a757da78dd4aa1b4a9b19cb011833730ccf2 Version: eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 Version: 829c49b6b2ff45b043739168fd1245e4e1a91a30 Version: 2f9761a94bae33d26e6a81b31b36e7d776d93dc1 Version: 4d55144b12e742404bb3f8fee6038bafbf45619d Version: 342debc12183b51773b3345ba267e9263bdfaaef Version: 342debc12183b51773b3345ba267e9263bdfaaef Version: 342debc12183b51773b3345ba267e9263bdfaaef Version: 7a742a9506849d1c1aa71e36c89855ceddc7d58e Version: e73c838c80dccb9e4f19becc11d9f3cb4a27d483 Version: a57fe60ef4cf96bfbb6b58397ec28bdb5a5c6b31 Version: 5.10.241 ≤ Version: 5.15.190 ≤ Version: 6.1.135 ≤ Version: 6.6.88 ≤ Version: 6.12.24 ≤ Version: 5.4.297 ≤ Version: 6.13.12 ≤ Version: 6.14.3 ≤ |
||
{
"containers": {
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"versionType": "git"
},
{
"lessThan": "5.10.261",
"status": "affected",
"version": "5.10.241",
"versionType": "semver"
},
{
"lessThan": "5.15.212",
"status": "affected",
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},
{
"lessThan": "6.1.178",
"status": "affected",
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{
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"status": "affected",
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{
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{
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],
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},
{
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{
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{
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"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
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"versionStartIncluding": "5.10.241",
"vulnerable": true
},
{
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"versionEndExcluding": "5.15.212",
"versionStartIncluding": "5.15.190",
"vulnerable": true
},
{
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"versionEndExcluding": "6.1.178",
"versionStartIncluding": "6.1.135",
"vulnerable": true
},
{
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"versionEndExcluding": "6.6.145",
"versionStartIncluding": "6.6.88",
"vulnerable": true
},
{
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"versionEndExcluding": "6.12.97",
"versionStartIncluding": "6.12.24",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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{
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{
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{
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{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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\u0027s qlen_notify callback will\nbe executed even though codel still has 1 packet on the queue and, thus,\nwill mistakenly deactivate the parent\u0027s 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": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:45:13.330Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74267",
"datePublished": "2026-08-15T05:57:42.263Z",
"dateReserved": "2026-08-15T05:44:03.878Z",
"dateUpdated": "2026-08-17T05:45:13.330Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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