FKIE_CVE-2026-74739
Vulnerability from fkie_nvd - Published: 2026-08-26 15:16 - Updated: 2026-10-30 13:20
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: cls_u32: skip hash tables in u32_bind_class()
u32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode
through the walker callback. u32_bind_class() unconditionally casts the
passed fh to tc_u_knode and accesses &n->res, so when fh is actually a
tc_u_hnode, which has no tcf_result member, this results in a
slab-out-of-bounds read of res->classid in tc_cls_bind_class().
The issue can be reproduced with the following commands:
tc qdisc add dev lo root handle 1: hfsc
tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit
tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1
tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit
Fix this by skipping hash tables via the TC_U32_KEY(handle) check.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/sched/cls_u32.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "43e1a952d534fc0e173b513a24b19ce99bb60974",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "07f57c7c47459e9bc75186b3af0fc2bc5be72f89",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "ec5f3005586a785689fd568361b0c5925cb1548b",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "19d114b93c94bdef70496f26685c2a6b242f41b3",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "594a064d603202b9ee21e07679d854e5c1750cc4",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "31f26a95eeee926946809ac456c61a3217936a62",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "e71f8e9ed6f311410b14741f6012afe01869c0fa",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
},
{
"lessThan": "6d3724e616faf952c3adcf8414fc21a828ef3709",
"status": "affected",
"version": "07d79fc7d94e3f884b8b1c95aa615b202bb5e4c1",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/sched/cls_u32.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.14"
},
{
"lessThan": "4.14",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.273",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.224",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.184",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.10",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: skip hash tables in u32_bind_class()\n\nu32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode\nthrough the walker callback. u32_bind_class() unconditionally casts the\npassed fh to tc_u_knode and accesses \u0026n-\u003eres, so when fh is actually a\ntc_u_hnode, which has no tcf_result member, this results in a\nslab-out-of-bounds read of res-\u003eclassid in tc_cls_bind_class().\n\nThe issue can be reproduced with the following commands:\n\n tc qdisc add dev lo root handle 1: hfsc\n tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit\n tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1\n tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit\n\nFix this by skipping hash tables via the TC_U32_KEY(handle) check."
}
],
"id": "CVE-2026-74739",
"lastModified": "2026-10-30T13:20:05.420",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-74739",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T19:15:59.810780Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-08-26T15:16:52.603",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/07f57c7c47459e9bc75186b3af0fc2bc5be72f89"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/19d114b93c94bdef70496f26685c2a6b242f41b3"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/31f26a95eeee926946809ac456c61a3217936a62"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/43e1a952d534fc0e173b513a24b19ce99bb60974"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/594a064d603202b9ee21e07679d854e5c1750cc4"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6d3724e616faf952c3adcf8414fc21a828ef3709"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/e71f8e9ed6f311410b14741f6012afe01869c0fa"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ec5f3005586a785689fd568361b0c5925cb1548b"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Nomenclature
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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