Vulnerability-Lookup

FKIE_CVE-2026-74696

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-08-25 06:18

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: tcp: fix TFO max_qlen accounting across reuseport migration A listener's TCP_FASTOPEN max_qlen stops being accurate and lets through far more pending Fast Open requests than it was configured for. This only shows up with SO_REUSEPORT listener migration, where closing a listener hands its still-pending TFO children over to a surviving one. fastopenq.qlen is charged in tcp_fastopen_create_child() when the child is created and uncharged in reqsk_fastopen_remove() when the handshake completes. The uncharge follows rsk_listener of the request the child points at, and inet_reqsk_clone() has repointed the child at a new request owned by the new listener, so the ++ and the -- land on two different sockets. The new listener's qlen drifts negative and its limit no longer binds. Charge the new listener during migration, like reqsk_queue_migrated() already does for queue->young and queue->qlen.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/inet_connection_sock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e98f0d80b9cccb5f828425d2004f9686e7d1ae24",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "b6247e0f96bd825ffb2005257f6177b5e642dee6",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "585fc5247d14939a561056aa2addd9b7c2b1f670",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "6e10ee56524a26b250229ad348637825646ddb88",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "a66e869cf0c90c1e47ae75f72b6482acbfc808ff",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "d974618b2097453778389d385e3741629c40e0a3",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "a0ab2ba83e35159d81cec830a92e885ecf8139be",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/inet_connection_sock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.14"
            },
            {
              "lessThan": "5.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.152",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.104",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "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\ntcp: fix TFO max_qlen accounting across reuseport migration\n\nA listener\u0027s TCP_FASTOPEN max_qlen stops being accurate and lets through\nfar more pending Fast Open requests than it was configured for.\n\nThis only shows up with SO_REUSEPORT listener migration, where closing a\nlistener hands its still-pending TFO children over to a surviving one.\n\nfastopenq.qlen is charged in tcp_fastopen_create_child() when the child\nis created and uncharged in reqsk_fastopen_remove() when the handshake\ncompletes.  The uncharge follows rsk_listener of the request the child\npoints at, and inet_reqsk_clone() has repointed the child at a new\nrequest owned by the new listener, so the ++ and the -- land on two\ndifferent sockets.  The new listener\u0027s qlen drifts negative and its\nlimit no longer binds.\n\nCharge the new listener during migration, like reqsk_queue_migrated()\nalready does for queue-\u003eyoung and queue-\u003eqlen."
    }
  ],
  "id": "CVE-2026-74696",
  "lastModified": "2026-08-25T06:18:53.137",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-22T16:16:44.153",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-74696 (GCVE-0-2026-74696)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:41

Title

tcp: fix TFO max_qlen accounting across reuseport migration

Summary

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/e98f0d80b9cccb5f8…
https://git.kernel.org/stable/c/b6247e0f96bd825ff…
https://git.kernel.org/stable/c/585fc5247d14939a5…
https://git.kernel.org/stable/c/6e10ee56524a26b25…
https://git.kernel.org/stable/c/a66e869cf0c90c1e4…
https://git.kernel.org/stable/c/d974618b209745377…
https://git.kernel.org/stable/c/a0ab2ba83e35159d8…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < e98f0d80b9cccb5f828425d2004f9686e7d1ae24 (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < b6247e0f96bd825ffb2005257f6177b5e642dee6 (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < 585fc5247d14939a561056aa2addd9b7c2b1f670 (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < 6e10ee56524a26b250229ad348637825646ddb88 (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < a66e869cf0c90c1e47ae75f72b6482acbfc808ff (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < d974618b2097453778389d385e3741629c40e0a3 (git) Affected: 54b92e84193749c9968aff2dd46e3b0f42643e18 , < a0ab2ba83e35159d81cec830a92e885ecf8139be (git)
Linux	Linux	Affected: 5.14 Unaffected: 0 , < 5.14 (semver) Unaffected: 5.15.216 , ≤ 5.15.* (semver) Unaffected: 6.1.183 , ≤ 6.1.* (semver) Unaffected: 6.6.152 , ≤ 6.6.* (semver) Unaffected: 6.12.104 , ≤ 6.12.* (semver) Unaffected: 6.18.45 , ≤ 6.18.* (semver) Unaffected: 7.1.9 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/inet_connection_sock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e98f0d80b9cccb5f828425d2004f9686e7d1ae24",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "b6247e0f96bd825ffb2005257f6177b5e642dee6",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "585fc5247d14939a561056aa2addd9b7c2b1f670",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "6e10ee56524a26b250229ad348637825646ddb88",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "a66e869cf0c90c1e47ae75f72b6482acbfc808ff",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "d974618b2097453778389d385e3741629c40e0a3",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            },
            {
              "lessThan": "a0ab2ba83e35159d81cec830a92e885ecf8139be",
              "status": "affected",
              "version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/inet_connection_sock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.14"
            },
            {
              "lessThan": "5.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.152",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.104",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.216",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.183",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.152",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.104",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.45",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.9",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix TFO max_qlen accounting across reuseport migration\n\nA listener\u0027s TCP_FASTOPEN max_qlen stops being accurate and lets through\nfar more pending Fast Open requests than it was configured for.\n\nThis only shows up with SO_REUSEPORT listener migration, where closing a\nlistener hands its still-pending TFO children over to a surviving one.\n\nfastopenq.qlen is charged in tcp_fastopen_create_child() when the child\nis created and uncharged in reqsk_fastopen_remove() when the handshake\ncompletes.  The uncharge follows rsk_listener of the request the child\npoints at, and inet_reqsk_clone() has repointed the child at a new\nrequest owned by the new listener, so the ++ and the -- land on two\ndifferent sockets.  The new listener\u0027s qlen drifts negative and its\nlimit no longer binds.\n\nCharge the new listener during migration, like reqsk_queue_migrated()\nalready does for queue-\u003eyoung and queue-\u003eqlen."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is in the inbound TCP SYN/TFO server path (tcp_v4_rcv/tcp_conn_request/tcp_try_fastopen), reachable by sending TCP Fast Open SYN packets to any internet-facing listener with server-side TFO enabled.\nAC:L - An attacker fully controls the TFO SYN flood; once a SO_REUSEPORT worker closes while TFO children are pending (routine nginx/k8s reloads), migration deterministically skews qlen negative with no narrow race or special memory layout required.\nPR:N - Exploitation needs only unauthenticated network reachability to the listening TCP port; no target credentials, capabilities, or local access are required because TFO SYN processing occurs before any application authentication.\nUI:N - No victim user action is needed beyond normal server operation; the remote attacker sends crafted TFO SYN traffic and benefits automatically when reuseport listener migration occurs during ordinary worker shutdown or reload.\nS:U - Impact is confined to the target host kernel TCP stack resource limits and availability; it does not cross VM, container, or IOMMU security boundaries to affect a different authority.\nC:N - The flaw is a signed counter accounting mismatch on fastopenq.qlen; it does not corrupt memory, leak kernel pointers, or provide an out-of-bounds read or use-after-free disclosure primitive.\nI:N - No arbitrary memory write, control-flow hijack, or unauthorized persistent data modification occurs; bypassing max_qlen only relaxes a rate limit while TFO cookie validation and normal TCP semantics still govern accepted data.\nA:H - With max_qlen disabled, a remote attacker can create far more pending TFO child sockets and SYN-carrying skbs than configured, exhausting kernel memory and socket tables and causing severe denial of service or OOM-induced host instability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:41:40.079Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24"
        },
        {
          "url": "https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6"
        },
        {
          "url": "https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670"
        },
        {
          "url": "https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88"
        },
        {
          "url": "https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff"
        },
        {
          "url": "https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3"
        },
        {
          "url": "https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be"
        }
      ],
      "title": "tcp: fix TFO max_qlen accounting across reuseport migration",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74696",
    "datePublished": "2026-08-22T15:32:58.414Z",
    "dateReserved": "2026-08-15T05:44:03.926Z",
    "dateUpdated": "2026-08-25T05:41:40.079Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
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.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.