CVE-2025-39766 (GCVE-0-2025-39766)
Vulnerability from cvelistv5
Published
2025-09-11 16:56
Modified
2025-09-11 16:56
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit
The following setup can trigger a WARNING in htb_activate due to
the condition: !cl->leaf.q->q.qlen
tc qdisc del dev lo root
tc qdisc add dev lo root handle 1: htb default 1
tc class add dev lo parent 1: classid 1:1 \
htb rate 64bit
tc qdisc add dev lo parent 1:1 handle f: \
cake memlimit 1b
ping -I lo -f -c1 -s64 -W0.001 127.0.0.1
This is because the low memlimit leads to a low buffer_limit, which
causes packet dropping. However, cake_enqueue still returns
NET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an
empty child qdisc. We should return NET_XMIT_CN when packets are
dropped from the same tin and flow.
I do not believe return value of NET_XMIT_CN is necessary for packet
drops in the case of ack filtering, as that is meant to optimize
performance, not to signal congestion.
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ▼ | Linux | Linux |
Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b Version: 046f6fd5daefac7f5abdafb436b30f63bc7c602b |
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|
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{
"containers": {
"cna": {
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{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/sched/sch_cake.c"
],
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"vendor": "Linux",
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{
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},
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{
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{
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"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.19"
},
{
"lessThan": "4.19",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.297",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.241",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.190",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.149",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.103",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.44",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.16.*",
"status": "unaffected",
"version": "6.16.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.17-rc3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "4.19",
"vulnerable": true
},
{
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},
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{
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}
],
"negate": false,
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit\n\nThe following setup can trigger a WARNING in htb_activate due to\nthe condition: !cl-\u003eleaf.q-\u003eq.qlen\n\ntc qdisc del dev lo root\ntc qdisc add dev lo root handle 1: htb default 1\ntc class add dev lo parent 1: classid 1:1 \\\n htb rate 64bit\ntc qdisc add dev lo parent 1:1 handle f: \\\n cake memlimit 1b\nping -I lo -f -c1 -s64 -W0.001 127.0.0.1\n\nThis is because the low memlimit leads to a low buffer_limit, which\ncauses packet dropping. However, cake_enqueue still returns\nNET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an\nempty child qdisc. We should return NET_XMIT_CN when packets are\ndropped from the same tin and flow.\n\nI do not believe return value of NET_XMIT_CN is necessary for packet\ndrops in the case of ack filtering, as that is meant to optimize\nperformance, not to signal congestion."
}
],
"providerMetadata": {
"dateUpdated": "2025-09-11T16:56:21.514Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c"
},
{
"url": "https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280"
},
{
"url": "https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e"
},
{
"url": "https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f"
},
{
"url": "https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb"
},
{
"url": "https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88"
},
{
"url": "https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3"
},
{
"url": "https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5"
}
],
"title": "net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2025-39766",
"datePublished": "2025-09-11T16:56:21.514Z",
"dateReserved": "2025-04-16T07:20:57.126Z",
"dateUpdated": "2025-09-11T16:56:21.514Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.1",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2025-39766\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-09-11T17:15:41.623\",\"lastModified\":\"2025-09-15T15:22:38.297\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit\\n\\nThe following setup can trigger a WARNING in htb_activate due to\\nthe condition: !cl-\u003eleaf.q-\u003eq.qlen\\n\\ntc qdisc del dev lo root\\ntc qdisc add dev lo root handle 1: htb default 1\\ntc class add dev lo parent 1: classid 1:1 \\\\\\n htb rate 64bit\\ntc qdisc add dev lo parent 1:1 handle f: \\\\\\n cake memlimit 1b\\nping -I lo -f -c1 -s64 -W0.001 127.0.0.1\\n\\nThis is because the low memlimit leads to a low buffer_limit, which\\ncauses packet dropping. However, cake_enqueue still returns\\nNET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an\\nempty child qdisc. We should return NET_XMIT_CN when packets are\\ndropped from the same tin and flow.\\n\\nI do not believe return value of NET_XMIT_CN is necessary for packet\\ndrops in the case of ack filtering, as that is meant to optimize\\nperformance, not to signal congestion.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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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.
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- 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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