← Back to CVE Explorer

CVE-2025-39766

Full vulnerability record from the local CVENow database.

Description

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.

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-11 17:15:41.623000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39766",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-09-11T17:15:41.623",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "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 configuración puede activar una ADVERTENCIA en htb_activate debido a la condición: !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 caída de paquetes. Sin embargo, cake_enqueue todavía devuelve NET_XMIT_SUCCESS, haciendo que htb_enqueue llame a htb_activate con un qdisc hijo vacío. Deberíamos 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 caída de paquetes en el caso del filtrado de ACKs, ya que eso está destinado a optimizar el rendimiento, no a señalar congestión."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "net/sched/sch_cake.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "7689ab22de36f8db19095f6bdf11f28cfde92f5c",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "de04ddd2980b48caa8d7e24a7db2742917a8b280",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "0dacfc5372e314d1219f03e64dde3ab495a5a25e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "710866fc0a64eafcb8bacd91bcb1329eb7e5035f",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "aa12ee1c1bd260943fd6ab556d8635811c332eeb",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "ff57186b2cc39766672c4c0332323933e5faaa88",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "62d591dde4defb1333d202410609c4ddeae060b3",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "046f6fd5daefac7f5abdafb436b30f63bc7c602b",
              "lessThan": "15de71d06a400f7fdc15bf377a2552b0ec437cf5",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "net/sched/sch_cake.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "4.19",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "4.19",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.4.297",
              "lessThanOrEqual": "5.4.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.241",
              "lessThanOrEqual": "5.10.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.190",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.149",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.103",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.44",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.16.4",
              "lessThanOrEqual": "6.16.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.17",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    },
    {
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
      "affectedData": [
        {
          "vendor": "Siemens",
          "product": "SIMATIC CN 4100",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "0",
              "lessThan": "V5.0",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-06-10T20:40:58.138217Z",
          "id": "CVE-2025-39766",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Primary",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "4.19",
              "versionEndExcluding": "5.4.297",
              "matchCriteriaId": "DB980BDC-B34E-41B6-BF6D-8AF3F2450143"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "5.5",
              "versionEndExcluding": "5.10.241",
              "matchCriteriaId": "D0D21C35-EB8A-488A-BBF9-403E4817E5DD"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "5.11",
              "versionEndExcluding": "5.15.190",
              "matchCriteriaId": "AD9E597F-3DDE-4D7E-976C-463D0611F13F"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "5.16",
              "versionEndExcluding": "6.1.149",
              "matchCriteriaId": "FDBE8280-8983-4D2D-943D-2E6D0104E2D8"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.2",
              "versionEndExcluding": "6.6.103",
              "matchCriteriaId": "F2293654-7169-49B5-8D0D-EE51EF8B8E48"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.7",
              "versionEndExcluding": "6.12.44",
              "matchCriteriaId": "12351F24-1133-4775-960C-F2B47E81298B"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "6.13",
              "versionEndExcluding": "6.16.4",
              "matchCriteriaId": "AFC28995-B8C3-4B68-8CB6-78E792B6629D"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*",
              "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"
            }
          ]
        }
      ]
    },
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*",
              "matchCriteriaId": "FA6FEEC2-9F11-4643-8827-749718254FED"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "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": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ]
    },
    {
      "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": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ]
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    }
  ]
}