CVE-2025-39766

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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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/sch_cake.c"], "versions": [{"version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b", "lessThan": "7689ab22de36f8db19095f6bdf11f28cfde92f5c", "status": "affected", "versionType": "git"}, {"version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b", "lessThan": "de04ddd2980b48caa8d7e24a7db2742917a8b280", "status": "affected", "versionType": "git"}, {"version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b", "lessThan": "0dacfc5372e314d1219f03e64dde3ab495a5a25e", "status": "affected", "versionType": "git"}, {"version": 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"operator": "OR"}]}], "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->leaf.q->q.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."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet/sched: Hacer que cake_enqueue devuelva NET_XMIT_CN cuando se excede el buffer_limit\n\nLa siguiente configuraci\u00f3n puede activar una ADVERTENCIA en htb_activate debido a la condici\u00f3n: !cl->leaf.q->q.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\nEsto se debe a que el memlimit bajo conduce a un buffer_limit bajo, lo que provoca la ca\u00edda de paquetes. Sin embargo, cake_enqueue todav\u00eda devuelve NET_XMIT_SUCCESS, haciendo que htb_enqueue llame a htb_activate con un qdisc hijo vac\u00edo. Deber\u00edamos devolver NET_XMIT_CN cuando los paquetes se descartan del mismo tin y flujo.\n\nNo creo que el valor de retorno de NET_XMIT_CN sea necesario para la ca\u00edda de paquetes en el caso del filtrado de ACKs, ya que eso est\u00e1 destinado a optimizar el rendimiento, no a se\u00f1alar congesti\u00f3n."}], "id": "CVE-2025-39766", "lastModified": "2026-10-19T21:10:00.160", "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": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-39766", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-06-10T20:40:58.138217Z", "version": "2.0.3"}}]}, "published": "2025-09-11T17:15:41.623", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0dacfc5372e314d1219f03e64dde3ab495a5a25e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/15de71d06a400f7fdc15bf377a2552b0ec437cf5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/62d591dde4defb1333d202410609c4ddeae060b3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/710866fc0a64eafcb8bacd91bcb1329eb7e5035f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7689ab22de36f8db19095f6bdf11f28cfde92f5c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/aa12ee1c1bd260943fd6ab556d8635811c332eeb"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/de04ddd2980b48caa8d7e24a7db2742917a8b280"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ff57186b2cc39766672c4c0332323933e5faaa88"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit", "id": "2394648", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2394648"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-39766", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-09-11T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39766\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39766\nhttps://lore.kernel.org/linux-cve-announce/2025091144-CVE-2025-39766-7465@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-09-12T08:02:40.120572+00:00", "updated": "2025-09-12T08:02:40.120628+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}