CVE-2026-90099 (GCVE-0-2026-90099)
Vulnerability from cvelistv5
Published
2026-09-17 16:06
Modified
2026-10-30 12:34
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: account classifier filter allocations to memcg
Allocations in the tc classifier *_change() paths (filter objects,
per-CPU counters, and per-filter aux data) use plain GFP_KERNEL without
__GFP_ACCOUNT, allowing unprivileged users to pin kernel memory outside
memcg charging. The shared tcf_exts_init_ex() action array allocation in
cls_api.c was also uncharged; this patch closes it along with the
per-classifier filter-object/percpu/aux allocations that remain
unaccounted.
Add GFP_KERNEL_ACCOUNT to:
- the shared tcf_exts_init_ex() action array (cls_api.c), common to every
filter of every classifier (32 pointers, 256 bytes);
- the filter-object, per-CPU-counter, and per-filter aux allocations in
cls_basic, cls_bpf, cls_cgroup, cls_flow, cls_flower, cls_fw,
cls_matchall, cls_route and cls_u32;
- the u32_init_knode() replace-path knode allocation (cls_u32.c), which
allocates the same struct tc_u_knode + sel.keys on every replace of an
existing knode and was missed by the create-path-only conversion.
Also fix the cls_basic error path: basic_change() inserts fnew into the
IDR before allocating the per-CPU counter. If alloc_percpu() fails the
errout path kfree'd fnew without idr_remove, leaving a dangling pointer
in the IDR. With GFP_KERNEL_ACCOUNT the percpu alloc becomes failable
on demand (memcg at memory.max), making the dead path attacker-reachable
and burning the handle permanently. Add the idr_remove on the percpu
failure path, matching the basic_set_parms failure-path pattern.
Note: vega@nebusec.ai provided a poc for basic_cls, but it was easy to
extend to the other classifiers.
Conditions to recreate the bug:
- CONFIG_NET_SCHED, CONFIG_NET_CLS_* (the classifier being used),
CONFIG_NET_CLS_ACT, CONFIG_MEMCG, CONFIG_USER_NS, CONFIG_NET_NS.
- Unprivileged user in a fresh user+network namespace (unshare -Urn),
or root with CAP_NET_ADMIN.
- Create a large number of tc filters (e.g. tc filter add dev lo
ingress ... <classifier> ...) while watching a memcg-limited cgroup:
system slab grows far faster than memory.current, pinning kernel
memory outside memcg charging.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 0da974f4f303a6842516b764507e3c0a03f41e5a Version: 0da974f4f303a6842516b764507e3c0a03f41e5a Version: 0da974f4f303a6842516b764507e3c0a03f41e5a Version: 0da974f4f303a6842516b764507e3c0a03f41e5a Version: 0da974f4f303a6842516b764507e3c0a03f41e5a Version: 0da974f4f303a6842516b764507e3c0a03f41e5a |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/sched/cls_api.c",
"net/sched/cls_basic.c",
"net/sched/cls_bpf.c",
"net/sched/cls_cgroup.c",
"net/sched/cls_flow.c",
"net/sched/cls_flower.c",
"net/sched/cls_fw.c",
"net/sched/cls_matchall.c",
"net/sched/cls_route.c",
"net/sched/cls_u32.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"versions": [
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{
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"programFiles": [
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"net/sched/cls_basic.c",
"net/sched/cls_bpf.c",
"net/sched/cls_cgroup.c",
"net/sched/cls_flow.c",
"net/sched/cls_flower.c",
"net/sched/cls_fw.c",
"net/sched/cls_matchall.c",
"net/sched/cls_route.c",
"net/sched/cls_u32.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.18"
},
{
"lessThan": "2.6.18",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.57",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
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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: account classifier filter allocations to memcg\n\nAllocations in the tc classifier *_change() paths (filter objects,\nper-CPU counters, and per-filter aux data) use plain GFP_KERNEL without\n__GFP_ACCOUNT, allowing unprivileged users to pin kernel memory outside\nmemcg charging. The shared tcf_exts_init_ex() action array allocation in\ncls_api.c was also uncharged; this patch closes it along with the\nper-classifier filter-object/percpu/aux allocations that remain\nunaccounted.\n\nAdd GFP_KERNEL_ACCOUNT to:\n- the shared tcf_exts_init_ex() action array (cls_api.c), common to every\n filter of every classifier (32 pointers, 256 bytes);\n- the filter-object, per-CPU-counter, and per-filter aux allocations in\n cls_basic, cls_bpf, cls_cgroup, cls_flow, cls_flower, cls_fw,\n cls_matchall, cls_route and cls_u32;\n- the u32_init_knode() replace-path knode allocation (cls_u32.c), which\n allocates the same struct tc_u_knode + sel.keys on every replace of an\n existing knode and was missed by the create-path-only conversion.\n\nAlso fix the cls_basic error path: basic_change() inserts fnew into the\nIDR before allocating the per-CPU counter. If alloc_percpu() fails the\nerrout path kfree\u0027d fnew without idr_remove, leaving a dangling pointer\nin the IDR. With GFP_KERNEL_ACCOUNT the percpu alloc becomes failable\non demand (memcg at memory.max), making the dead path attacker-reachable\nand burning the handle permanently. Add the idr_remove on the percpu\nfailure path, matching the basic_set_parms failure-path pattern.\n\nNote: vega@nebusec.ai provided a poc for basic_cls, but it was easy to\nextend to the other classifiers.\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED, CONFIG_NET_CLS_* (the classifier being used),\n CONFIG_NET_CLS_ACT, CONFIG_MEMCG, CONFIG_USER_NS, CONFIG_NET_NS.\n- Unprivileged user in a fresh user+network namespace (unshare -Urn),\n or root with CAP_NET_ADMIN.\n- Create a large number of tc filters (e.g. tc filter add dev lo\n ingress ... \u003cclassifier\u003e ...) while watching a memcg-limited cgroup:\n system slab grows far faster than memory.current, pinning kernel\n memory outside memcg charging."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:34:07.767Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/8a622d5b4d81c1572f42bbf3fb823b6e63d44dae"
},
{
"url": "https://git.kernel.org/stable/c/5fbb06d4f3d4c509ffe95572384a498bf319e5bf"
},
{
"url": "https://git.kernel.org/stable/c/bf6006cea193cf065f7a64fc7974247f8112af33"
},
{
"url": "https://git.kernel.org/stable/c/68fb30607169c92de57c5c82b6af8a733af1cc09"
},
{
"url": "https://git.kernel.org/stable/c/18c68c8f3d3ff0a4def1391021b439c4333a6c71"
},
{
"url": "https://git.kernel.org/stable/c/1beb81947eb486716af80db7a584f9e9fef7e003"
}
],
"title": "net/sched: account classifier filter allocations to memcg",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-90099",
"datePublished": "2026-09-17T16:06:10.858Z",
"dateReserved": "2026-09-11T19:38:34.786Z",
"dateUpdated": "2026-10-30T12:34:07.767Z",
"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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