FKIE_CVE-2026-63913

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-20 15:16
Severity
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number. Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction. As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended. So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2006979a15af5404bf932a325357683c0bac1656
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6476c17d536dbd321c073242e762ddb2713a1238
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b98ab51c45c5608a1c19ce7fd17a3032469bb83f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d67c6adee8d1b65330d0174c4c367faba14e80a8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f206def4e86d810f927ba1d8e322ea72b29bce58
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f5547bebc416d56f56fb5b86dc20aabfa42165a0
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_proto_tcp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2006979a15af5404bf932a325357683c0bac1656",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "6476c17d536dbd321c073242e762ddb2713a1238",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "f5547bebc416d56f56fb5b86dc20aabfa42165a0",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "f206def4e86d810f927ba1d8e322ea72b29bce58",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "b98ab51c45c5608a1c19ce7fd17a3032469bb83f",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "d67c6adee8d1b65330d0174c4c367faba14e80a8",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            },
            {
              "lessThan": "bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a",
              "status": "affected",
              "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_proto_tcp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.15"
            },
            {
              "lessThan": "2.6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "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\nnetfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check\n\nAn unintended behavior in the TCP conntrack state machine allows a\nconnection to be forced into the CLOSE state using an RST packet with an\ninvalid sequence number.\n\nSpecifically, after a SYN packet is observed, an RST with an invalid SEQ\ncan transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of\nwhether the RST corresponds to the expected reply direction. The relevant\ncode path assumes the RST is a response to an outgoing SYN, but does not\nvalidate packet direction or ensure that a matching SYN was actually sent\nin the opposite direction.\n\nAs a result, a crafted packet sequence consisting of a SYN followed by an\ninvalid-sequence RST can prematurely terminate an active NAT entry. This\nmakes connection teardown easier than intended.\n\nSo, tighten the state transition logic to ensure that RST-triggered\nCLOSE transitions only occur when the RST is a valid response to a\npreviously observed SYN in the correct direction."
    }
  ],
  "id": "CVE-2026-63913",
  "lastModified": "2026-07-20T15:16:55.423",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T16:17:09.237",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2006979a15af5404bf932a325357683c0bac1656"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6476c17d536dbd321c073242e762ddb2713a1238"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b98ab51c45c5608a1c19ce7fd17a3032469bb83f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d67c6adee8d1b65330d0174c4c367faba14e80a8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f206def4e86d810f927ba1d8e322ea72b29bce58"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f5547bebc416d56f56fb5b86dc20aabfa42165a0"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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