CVE-2026-68118

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: tcp: challenge ACK for non-exact RST in SYN-RECEIVED The SYN-RECEIVED request-socket path in tcp_check_req() accepts an in-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A non-exact RST therefore removes the request instead of eliciting a challenge ACK. RFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in SYN-RECEIVED: an exact RST resets the connection, while a non-exact in-window RST must trigger a challenge ACK and be dropped. Apply that check before the ACK-field validation, following the RFC sequence-number, RST, then ACK processing order. Factor the per-netns challenge ACK quota out of tcp_send_challenge_ack() so request sockets can share it. Use the request socket's send_ack() callback and its own out-of-window ACK timestamp to send and rate-limit the response.

Severity

HIGH

CVSS score

8.2 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-08-10 13:19:56.850000

Last modified

2026-10-30 13:19:40.740000

View original CVE JSON

{
  "id": "CVE-2026-68118",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-08-10T13:19:56.850",
  "lastModified": "2026-10-30T13:19:40.740",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: challenge ACK for non-exact RST in SYN-RECEIVED\n\nThe SYN-RECEIVED request-socket path in tcp_check_req() accepts an\nin-window RST without requiring SEG.SEQ to exactly match RCV.NXT.  A\nnon-exact RST therefore removes the request instead of eliciting a\nchallenge ACK.\n\nRFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in\nSYN-RECEIVED: an exact RST resets the connection, while a non-exact\nin-window RST must trigger a challenge ACK and be dropped.\n\nApply that check before the ACK-field validation, following the RFC\nsequence-number, RST, then ACK processing order.  Factor the per-netns\nchallenge ACK quota out of tcp_send_challenge_ack() so request sockets\ncan share it.  Use the request socket's send_ack() callback and its own\nout-of-window ACK timestamp to send and rate-limit the response."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "include/net/tcp.h",
            "net/ipv4/tcp_input.c",
            "net/ipv4/tcp_minisocks.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "c5dc463cc60eb26079b19607c9dbda76491dad05",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "0fe4636665d14a258de70b4f3e8248e6d42038f1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "234f9ffbd9b2c1b24ec67200ea3cff07401bec48",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "22cec809b048495310f206d9abbcdbbfbdce3ae3",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "282f23c6ee343126156dd41218b22ece96d747e3",
              "lessThan": "a28c4fcbf774e23b4779cae468e3497a5ad1f4a1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "86791bbfe5ed7b275be040cfeff049a1624af1b7",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "61f69dc4e40e41b0018f00fa4aeb23d3239556fb",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "34fb350281ced2a72707a5c0064f69992d440edb",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3.0.58",
              "lessThan": "3.1",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "3.2.37",
              "lessThan": "3.3",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "3.4.25",
              "lessThan": "3.5",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "include/net/tcp.h",
            "net/ipv4/tcp_input.c",
            "net/ipv4/tcp_minisocks.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "3.6",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "3.6",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.153",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.105",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.42",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.1.6",
              "lessThanOrEqual": "7.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T15:44:08.841575Z",
          "id": "CVE-2026-68118",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0fe4636665d14a258de70b4f3e8248e6d42038f1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/22cec809b048495310f206d9abbcdbbfbdce3ae3",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/234f9ffbd9b2c1b24ec67200ea3cff07401bec48",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a28c4fcbf774e23b4779cae468e3497a5ad1f4a1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/c5dc463cc60eb26079b19607c9dbda76491dad05",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}